Starting Construction

We will be starting with the System, RS-232, Power Supply, and Test sections of the schematic from the last lesson. This requires the parts outlined by dashed lines on the schematic (the ones you really need are listed later in this lesson. In the last lesson I furnished you with a help file zip that contains the pinouts of all the chips. You will need this to make the connections between the chips. I would read completely through this lesson once before I started doing anything outlined in it.

There will be some soldering involved with building the power supply. The way I did it was to cut off the connector on the end of the transformer (T702-ND) cable, if there is one, and solder the cable to the two pins on the bridge(W005G-ND) marked ~, leaving the cable from the transformer as long as possible. Then solder the 470 UF (P4234-ND) cap across the + and - terminals of the bridge, observing the polarity of the cap, leaving all the leads on the bridge intact, not cutting any of them. The cap has a stripe down one side with an arrow pointing to the - lead of the cap. Connect this to the - lead of the bridge and the other to the + lead of the bridge. Place the cap as close as possible to the bridge, leaving the leads of the bridge as long as possible. Bend the + and - leads of the bridge so that they line up with the IN and GND leads of the 7805 (NHM7805FA-ND) regulator, but don't touch any of the other leads of the bridge.

Then slip the heat sink (HS121-ND) on to the 7805. I had a little trouble with this as the clearance inside the heat sink was too tight initially to slip it onto the 7805. I spread out the fins of the heat sink, which opened up the clearance for the 7805. One end of the heat sink clearance is thicker than the other end. The thinnest end is where the metal tab of the 7805 slips into and the thicker end is where the body of the 7805 ends up. Bend out the fins of the heat sink just enough to slip in the 7805, metal tab first, into the thickest end. Slide in the 7805 until the metal tab ends up at the other end of the heat sink. One end of the heat sink will now be pressed against the metal tab and the other end will be pressed against the body of the 7805. This should be as tight a fit as you can get, the tighter it is the better the heat will be conducted and radiated away from the 7805.

Solder the + lead of the bridge to the IN lead of the 7805 and the - lead of the bridge to the GND lead of the 7805. Then solder a solid #24 or #26 wire to the OUT lead of the 7805 and another to the - lead of the bridge, somewhere between where the cap is connected and where the 7805 is connected. These wires should be a foot long or so. Now connect two more wires to the ~ leads of the bridge, somewhere in the middle between where the transformer is connected and the body of the bridge. I would use red for the OUT lead of the 7805, black for the - from the bridge, and two other colors for the ~ leads of the bridge. An alternate source for the wire needed is to strip out a foot of "silver satin" phone cord. This is the very same flat cord that is usually used between your phone and the receptacle that it plugs into. This is stranded, four color (red, green, yellow and black) wire that works perfect for this and you will need some for the RS-232 cable that goes to the PC anyway. I would get at least 25 feet and possibly 50 feet of this cable. It is cheap and is available at many places. This is the flat silver grey looking phone cable. It comes in white and beige also. Some of it doesn't have multi colored wires inside. I would avoid this type in preference to the four color cable. When you make the serial cable you need the color coded wire to do it right.

Now what you appear to have is a "spider web" of parts, with the leads of the transformer coming in from one side, and four wires coming off of the other side. This is EXACTLY what you want. None of the leads that aren't soldered to each other should be touching each other. Bend the leads to place at least an 1/8th of an inch clearance between them.

What I did next was to take a "hot glue gun" and stick the transformer leads just before they connect to the bridge down to a 18" piece of 1" by 6" wooden board, near one end. Put enough glue to secure the transformer leads so they won't pull loose by tugging on the transformer lead. This type glue sets very fast so after you squeeze out a puddle of glue, a half inch in diameter or so, stick the transformer leads into the puddle with the leads going to the transformer pointing out away from the board, and do it while the glue is still molten. By the way, the glue is VERY HOT so don't put your fingers into it, ouch!!! I then squeezed out a little more and covered over the transformer leads. This glue sticks well to EVERYTHING and is a handy thing to have around for repairs of all kinds.

The Super Strips (protoboards) have a peal off stickum' on the back. What I did next was to peal off the covers and stick down these strips, side by side (not end to end), centered both ways on the board, the longest dimension of the protoboard running in the same direction as the long dimension of the board. Running down each side of the strips are two lines of connections, that are normally used for power buses. I normally use the outside bus on either side as the positive (VCC) bus and the inside on either side as the negative (GND) bus. This means that down each side of each protoboard you will have both a VCC and a GND bus, side by side.

Now all this may seem rather crude, putting such high tech stuff on a piece of wood, but I like the wood in preference to most other things. It's usually easy to obtain, cheap, and most of all it weighs enough to give a solid base for everything that won't move around every time you tug on a wire. Plus it's easy to screw into with small wood screws, drill, and it's non-conductive. If you don't want to use hot glue, you can fasten the power supply down however, or even mount it on a perf board (a board with holes on .1" centers and copper pads on the back side to solder to). You insert the parts on the bare side and solder them on the back side. Then make the interconnections, usually using the leads of the parts by bending them over.

I thought about all this as I made mine, and chose to do it the way I described to you above. It is bare bones, fairly cheap, and I just like wood! But some of you may like more esthetically pleasing packaging than this. Do it however you choose, only keep it electronically as I have described.You can spruce it up with an on/off power switch, by running one lead from the transformer through it. I just unplug the transformer from the wall when I want to turn it off. The fewer the parts, the less to go wrong.

Next comes the RS-232 cable. Using about a 10 to 15 foot length of flat phone cord, strip off about 3 inches of the silver PVC coating, exposing the four color wire inside, taking care not to remove any insulation off of the colored wires as you remove the silver coating. You can do this by CAREFULLY slicing down the 3 inch length on one of the flat sides, not cutting too deep or by using a pair of diagonal cutters gripping the wire with the cutters at the 3 inch mark and pulling away from the rest of the length of cable. The correct amount of pressure needs to be applied with the cutters to grip the flat insulation tight enough to pull it off while not gripping it so tight that you pull off the colored insulation from the wire inside. You may have to try more than once to get it right.

Using the same technique, remove a foot of the flat insulation from the other end, 3 or 4 inches at a time. Now comes the female connector the will end up plugging into the serial port on the PC. There are two possible connectors that you will be using, either a 9 pin or a 25 pin female "D" connector. The D comes from the fact that the shape of the connector resembles the letter D, wider on one side than the other. Which one you use depends on the available serial connectors on your PC. Some have a 9 pin, some have the 25 pin, and some have both. If you have a modem installed inside your PC, there is a possibility that if you have both 9 and 25 pin versions, that the 25 pin one has been disabled. Your mouse may be plugged into the 9 pin one, leaving you no connectors to plug into. That is the way my machine is. So when I play with the micro, I unplug the mouse (since it's not used), plug in the micro and reboot the machine, if I've been using it, to eliminate the mouse driver being loaded. Otherwise just unplug the mouse and plug in the micro and turn on your machine.

If you automatically start up WINDOWS when the power is turned on, it will still start up without a mouse. After it finishes starting up just press CTRL and the F4 key and if you are using WIN31, you will get a message asking you if you want to exit windows, answer yes. In a few seconds,you will be at the DOS command line. If you are using WIN95, a different window will pop up with four options listed. The third one down is to restart the computer in the MSDOS mode. The SHUTDOWN option will be selected when the window first comes up but you can use the down arrow key to move the dot to the RESTART in MSDOS mode option. Then hit enter. After a few seconds, you will be at the DOS prompt. An alternative for WIN95 is when the "Starting Windows 95" message appears, immediately press the F8 key. You will be presented a multi option menu with one of the options being "Command prompt only". Down arrow to highlight that option and press enter. In a few seconds you will be at the DOS command line.


To digress just a minute. I haven't spoken much of the technique of soldering but I take this time to do it now. Soldering is an art that is developed with time. The basic rule is to apply the tip (the heat) on one side of whatever and the solder to the other side. This causes the solder to "wick" or be drawn toward the tip after it melts, wetting whatever is in between. Another rule is to "tin" each piece that is to be joined by soldering. Tinning is simply applying solder to each piece, individually, before you solder them together. Another technique is called "twist and tin". This applies to stranded wire. To twist and tin stranded wire, strip off a small amount of insulation from the wire. This exposes the separate strands of small wire that make up the stranded wire. Now grip the exposed wire, which will usually fray out a little when you strip it, between your thumb and finger and apply a twisting action to tightly twist the strands back together. They will usually be slightly twisted, indicating the direction of the twist imparted to them during manufacture. This is the same direction you want to twist them. It doesn't take much to twist the soft copper back together. You only need enough twist to hold all the small wires together in a bundle. They will usually form the desired twist by pressing together your thumb and finger on the wires, and in a twisting motion, in one direction or the other, slowly slipping your thumb and finger off of the end of the wire, never letting up on the pressure. Examine the bundle afterward, and likely as not, they will be nicely, slightly twisted and together in a fairly compact spiral. It doesn't matter if at the very end there may still be a little fraying. You will cut that off after tinning. Now apply the tip to one side of the wire while applying the solder to the other side. If everything is right, the solder will almost immediately start to melt and wick into the twisted wires, making a solid wire out of the small separate wires when the solder cools. As soon as you see the solder completely wick into the wires, you can remove the tip, letting the wire cool. You have just "twisted and tinned" the stranded wire. You should try to not kink the wire in the process of twisting it, but rather have a fairly straight bundle of wires before you tin it. Also, if I say to strip, twist and tin an 1/8" of a wire, you need to really start with a 1/4" and then cut it off to the right length when you finish tinning it. In other words, the dimensions I give you are "finished" dimensions.

With both pieces having been tinned, you put them together and apply the tip to the junction and the two pieces will join, the solder on each piece melting into the other, wicking into the space between the pieces. As soon as this happens, remove the heat and let it cool, holding the parts perfectly still until they become solid.Any movement during this cooling down period will increase the odds that you won't have a good connection afterwards. The soldered joint should have a good shine to it. If it looks dull, redo it until it shines. The shorter time you have to keep the heat applied, the better. That is the art of it, doing it with as little heating time as possible. You create less fumes and lesson the risk of doing damage to more temperature sensitive parts.

It is also sometimes necessary to apply a minute amount of solder to the tip itself, so that when you bring it in contact with something else, the heat is transferred to the something else at a faster rate, due to the melted solder conforming to the shape of the something else better. Also, there is usually a sponge, dampened with water, that is used to clean off the tip, from time to time. You should keep the tip with a shine on it, by wiping it with a light pressure across the sponge as you slightly rotate the tip, wiping off any excess solder. Then apply a small amount of fresh solder to the tip, just a very small amount.

About the solder. You should always use resin core solder, of the smallest diameter that you can get. If you buy it in a consumer electronics store like Radio Shack, it will be of this type. The other type is acid core, used to join copper pipe together. This is what you will find in a plumbing store. Don't use this type for electronic soldering. The resin in the center of the solder acts as a cleaning agent, which helps the solder to cling to the copper and to wick. The resin will wick toward the heat, bringing the solder with it. This is why you clean the tip every so often, to keep a supply of fresh solder, with its corresponding resin content, on the tip. The resin turns to a type of steam, the smoke you see rising from the melting solder. It is very pungent and should not be breathed directly. Hold your breath at the moment you contact the tip or part with the solder, and the most smoke occurs, until you remove the heat and the smoke subsides. You can also move back away after removing the heat, and with a small amount of air circulation, avoid breathing most of the fumes. Although I can't prove it, I think that the fumes quickly return to a solid and precipitate out of the air, and don't linger very long.

Now back to the "D" connector. You need something to hold the connector with while you both bring the tinned wire into contact with the "cup" (the back side of the connector) while at the same time pressing the tip against the previously tinned cup, all at the same time. What has worked for me is a pair of slip joint pliers (one trade name is Channel Locks). These pliers have several positions for the hinge point, giving more or less spacing between the jaws, allowing you to grip parts of varying thickness. Slip the joint so that the jaws are just wide enough to hold the connector with a little pressure. Take a fairly thick rubber band, or a couple of skinny ones, and make several loops around the handles, which will keep enough tension in the jaws to hold the connector without you having to hold them together with your hand. Now take a second pair of pliers, whatever kind, and put several wraps of rubber band on those handles and then open up the jaws and clamp onto the handle of the first pair, at a right angle. This will create a stable combination that will free stand on the table and hold the connector in place, with enough weight to keep it steady while you solder to it.

Following is the pinout of both varieties of serial connectors. The pins number from left to right (viewed from the back) with the numbers starting on the row with the most pins, continuing on with the next row, left to right.

9 Pin Female                                     25 Pin Female

1       5             1                       13
o o o o o             o o o o o o o o o o o o o
 o o o o               o o o o o o o o o o o o
 6     9              14                     25

               (Viewed from the solder side)

9 Pin connector directions

Cut three lengths of wire, whatever kind, about an inch long and strip, twist (if it's stranded) and tin about an 1/8" on all the ends. Now tin all but pin 9 on the connector, which is unused. Now solder one end of one of the wires to pin 1. Solder another to pin 6. Now take the two loose ends and solder both of them to pin 4. That completes the first set of jumpers. Now take the last wire and solder it to pin 7 and the other end to pin 8. Now take the flat phone cable and strip, twist, and tin the red, green, and black wires about an 1/8" on the end that you stripped off the 3" of insulation. Leave the yellow wire untouched. Now solder the red wire to pin 2, the green to pin 3 and the black to pin 5.

25 Pin connector directions

Cut three lengths of wire, whatever kind, about 1-1/2" long and strip, twist (if it's stranded) and tin about an 1/8" on all the ends. Now tin pins 2,3,4,5,6,7,8, and 20 on the connector. Solder one end of one of the wires to pin 8. Solder another to pin 6. Now take the two loose ends and solder both of them to pin 20. That completes the first set of jumpers. Now take the last wire and solder it to pin 4 and the other end to pin 5. Take the flat phone cable and strip, twist, and tin the red, green, and black wires about an 1/8" on the end that you stripped off the 3" of insulation. Leave the yellow wire untouched. Now solder the red wire to pin 3, the green to pin 2 and the black to pin 7.

If you didn't get a hood for the connector, your done with the PC end of the cable. Otherwise, if the hood you bought was the one listed, tie a knot in the flat cable as close as you can to the end of the flat insulation on the connector end. Thread the cable through one of the rubber strain reliefs (the one that best fits the cable) starting at the end that fits inside the hood (it has a lip around it), until the knot is up against it. Lay half of the hood on the table and fit the strain relief into place (there is a groove for the lip to fit into), then fit the connector in its place (right at the end of the hood, but still inside just a little). There is a lip in the hood, right at the end that the flange around the connector fits into. During this last step, it will be necessary to bend and adjust the wires a little to fit them in between the connector and the strain relief, squeezing them so that they fit inside the hood. Holding the pieces in place, take the other half of the hood and fit it together with the first. There should be no wires caught or sticking out around the hood, and the connector should be visible at the end of the hood, and the end of the strain relief should be sticking out the other end, a quarter inch or so, along with the cable.

If you managed all this, you're just about finished with this balancing act. Now take the two longer, fully threaded screws that came with the hood, and insert one into one of the holes, through the hood. Take one of the nuts and place it on the opposite end of the screw. Notice that the hood has different looking indentions on either side of where you inserted the screw. The head of the screw should be in the round indention and the nut should be fitted into the hex shaped indention. Now press the nut into the hex indention, which will force the screw out a little on the other side. Use your small flat bladed screw driver and screw the screw into the nut, keeping the nut pressed in as far as it will fit, until the screw starts. This keeps the nut level with the end of the screw, so it will start into the nut without cross threading. If the screw seems to get tight with just a single turn of the screw driver, you have started the screw in crossed. Back the screw out until you feel it clicking against the nut and start it in again. There should be no resistance when starting the screw into the nut. By the way, for those who don't know, turning the screw clockwise screws in the screw and counter - clockwise unscrews it, or backs it out. Notice that there is one round indention and one hex shaped indention on each surface of the hood. I won't insult your intelligence by explaining what this means other than to say the nuts go into the hex shaped indentions. Insert the other screw and nut and screw them together. Now tighten the screws until they are snug, watching all the time that there are no wires caught in the junction of the two halves of the hood. When you finish, you should have a very nice, heavy, cast zinc, RS-232 connector with a 10 or 15 foot cable attached. The connector should be held in place, sticking out the end of the hood, with the flange of the connector held firmly by the two lips at the end of the hood. The strain relief should be sticking out the cable end about a quarter of an inch or so, hopefully, with the cable leaving the strain relief. On the other end of this cable, the end you stripped a foot of flat insulation from, strip, twist, and tin 1/4" on the red, green, and black wires.

The Load and Break switches

The last thing are the two switches. Strip out about a foot of the flat phone cable for each switch. and use the red,green, and black wires. Strip, twist, and tin about a 1/4" of wire on each end of the six wires. These switches were intended to be mounted on a printed circuit board and that is why they have leads that bend together in one direction and end up level on the end. If you were to straighten out these leads one would be longer than the rest. DON'T straighten them out, but solder the red wire to this lead. Solder the green to the next, and the black to the last. What I did now was to put a small spot of glue on the board and stick the first switch down, with the handle of the switch (the part you flip to switch positions) where it sticks out past the edge of the the front surface of the board (the one that will be closest to you when you place it on the table or where ever you finally put it), towards the end that you stuck the transformer cable down, with the two metal tabs that were meant to fit into a printed circuit board, pointing to the right. Repeat this for the other switch, placing them about 2" apart. Now print on the board on the left side of the left switch the word "LOAD". On the right side of left switch the word "RUN". On the left side of the right switch the word "BREAK" and on the right side of the right switch the word "NORMAL". Print these words as close to the front surface of the board as you can so that they can be easily seen by you.

I would finish by using the glue gun to stick the RS-232 cable down to the board. Do this at about 1 or 2 inches back from the stripped out part of the cable, and somewhere near where you stuck down the transformer cable, with the cable going to the PC pointing away from the board. This should leave about a foot of loose wire to connect to the protoboard.


Boy am I glad that's over with. I've dreaded having to explain all this, wanting to explain it thoroughly enough for the novice, but not insult the more experienced at the same time. I probably failed on both accounts. I would like to assume that anyone attempting this has had some experience, but I have to assume that some have not. I hope that I was clear enough for all.

As promised, here are the bare minimum parts needed to complete this lesson.

1      T702-ND             9V AC 600MA WALL TRANSFORMER
1      HS121-ND            TO-220 HEAT SINK FOR 7805
1      W005G-ND            BRIDGE RECTIFIER
1      P5234-ND            470UF 16VDC ELECTROLYTIC CAP
1      NHM7805FA-ND        5 VOLT REGULATOR
1      SE1232-ND           11.0592 MHZ OSCILLATOR
1      CD74HCT04E-ND       HEX INVERTER
10     P2040-ND            22UF 16VDC TANTALUM CAP
2      CKN1059-ND          SPDT SWITCH
1      2N3904-ND           NPN TRANSISTOR
5      330EBK-ND           330 OHM 1/8TH WATT RESISTOR
5      470EBK-ND           470 OHM 1/8TH WATT RESISTOR
10     10KEBK-ND           10K OHM 1/8TH WATT RESISTOR
1      923252-ND           PROTOBOARD
1      4N35QT-ND           OPTOISOLATOR
3      HLMP-1700QT-ND      LED
10     BAV21DICT-ND        DIODE
1      P2105-ND            1UF 16VDC TANTALUM CAP

Depending on whether you use a 9 pin or 25 pin RS-232 connector:

1      109F-ND             9 PIN FEMALE "D" SERIAL CONNECTOR
1      125F-ND             25 PIN FEMALE "D" SERIAL CONNECTOR
1      909Z-ND             9 PIN HOOD
1      925Z-ND             25 PIN HOOD

I only listed 1 of the protoboards so if you just get 1, make sure when you place it on the board, that you leave room for the second one when its placed on the board (you will need two before we're through). All wires that plug into the protoboard should be no larger than #24 solid wire. The end that plugs into the protoboard should be stripped (twisted and tinned if stranded) about 1/4"

The first step is to connect the power supply to the protoboard.Plug the end of the red wire into the outside bus strip on whichever side you wish. Plug the black one into one of the inside strips. Then make two jumpers long enough to span the distance from one side of the protoboard to the other and jumper the two inside strips together and the two outside strips together. Both sets of busses are really divided in half in the middle of the protoboard. You need to make four jumpers about an inch long and plug them across the wider gap in the center on either side of the protoboard to make the busses run the complete length of the protoboard. The design idea behind the protoboard was to have 8 busses, four on either side, that run halfway down the length of the protoboard. But we need to join them together, in the middle, to make 4 busses, two on either side, that run the full length of the protoboard. You'll notice in each buss strip, there are 10 sets of 5 holes each, separated by a small gap between each set. But in the center of the protoboard, these gaps are larger than the rest. This is where you need the short jumpers.

At this point you have a protoboard with 2 power busses running along the full length of the protoboard, on either side, the inside ones are GND and the outsides ones are VCC. Remember this when connecting power to a chip. The inside bus is ground and the outside bus is +5 volts. If you bought both protoboards you need to double the recipe and then jumper the inside bus on one protoboard to the inside bus on the other. Do the same with the outside busses on each protoboard.

Check your connections, both to the protoboards and in the supply itself. Refer to the help files to verify the pinout of the 7805 and check it against the way you wired up the supply. Check to make sure that the AC from the transformer is connected to the leads on the bridge marked ~. Make sure that the + from the bridge is connected to both the + side of the CAP and the IN lead of the 7805. Make sure the - lead of the bridge is connected to the - lead of the CAP and the GND lead of the 7805. The 7805 is short circuit protected so if there was a mistake, it shouldn't hurt anything. The polarity of the 470uf CAP is important. The + side of the CAP must be connected to the + lead of the bridge and the - lead to the - lead of the bridge, or damage could result to the CAP (it could pop when you apply power).

Put on your safety glasses and power up the supply and measure the +5 volts to make sure it's working. Then verify that all the busses are powered up with the correct readings on each. The multimeter should be set to read DC voltage. If it has a range switch, set it to one that will allow you to measure +5 volts without over ranging the voltmeter. The cheaper ones are auto ranging and only need to be set to the right function, DC volts. By the way, I was wrong about the price of a cheap multimeter. I guess it's been several years since I bought one and the one I was thinking of at Radio Shack is really $40 (still a good buy, but you might check around and find one a little cheaper, it needs to be digital, though, with a display, not a meter needle). The red lead of the meter should be connected to the VCC bus and the black one to the GND bus. If you don't get a reading of between 4.9 to 5.2 volts, something is wrong. Turn off power and re-check your connections. There arn't too many places that a problem could be. The most common is that wires are touching that arn't supposed to be. The second most common is that the outlet you plugged the wall transformer into isn't hot (you would have gotten a reading of 0). The third most common is that you reversed the connections to the 7805, with the IN and OUT switched (the reading didn't fall within the range of 4.9 to 5.2 volts).

A trouble shooting proceedure for this would be to turn on power and measure the AC voltage at the two ~ leads on the bridge. It should read between 9 and 11 volts. If this is good, measure the DC volts across the + and - leads of the bridge. It should read between 12 and 14 volts. If this is good then measure from the OUT lead on the 7805 and the - lead on the bridge. You should get between 4.9 and 5.2 VDC. If this is good, you've got no problems with the supply and the problem is the wires from the power supply to the protoboard.

If you were lucky and you got a good reading for the power on all the busses, then it is time to proceed to plugging in parts. Notice that while the power strips run in the direction of the length of the protoboard, the holes in the center of the protoboard seem to be all together, side by side with a dividing strip down the middle, running the full length of the protoboard, seperating them into two large areas. What really is the case is that the whole protoboard is arranged into sets of five holes, just like the power strips. Only in the case of the two large areas of holes, the sets of five occur as strips radiating outward in either direction, from the dividing strip down the middle. So the sets of five run perpendicular to the power strips on either side of the divider. I will try to draw this below (I hope this drawing doesn't straddle a page break. If it does, put the two sheets together to see what I'm trying to show.

----- ----- ----- ----- ----- J ----- ----- ----- ----- ----- VCC BUS
----- ----- ----- ----- ----- J ----- ----- ----- ----- ----- GND BUS


----- ----- ----- ----- ----- J ----- ----- ----- ----- ----- GND BUS
----- ----- ----- ----- ----- J ----- ----- ----- ----- ----- VCC BUS

This isn't a perfect representation of the protoboard but it should clarify what I'm trying to show. The chips are plugged in straddling the divider running down the middle. This means that half of the pins will be plugged into one side of the divider and the other half will be plugged into the other side of the divider. Where the letter "J" is, this is where the power busses are jumpered so that they become two single busses that run the length of the protoboard. Referring to the Pinout Sheets, Page 1, a chip will have an indentention in the middle of one end OR it will have a small dot or indention next to pin 1.

With power turned off, plug in the dual single shot chip (CD74HCT123E-ND, with the indent to the left. Although I won't say it for the other chips, always plug in the chips with the indent to the left. Also the -ND is a naming scheme use by DigiKey and will be dropped in this discussion. Looking at the drawing above, that would place pin 1 of the chip plugged into the first strip of five points in the lower area, first row on the far left. Since this is an 16 pin dip, the first 8 rows on either side of the divider are used up. When you plug in a chip, one of the narrow variety, you use up 1 of the five tie points in each strip, leaving only 4 that can be connected to with jumpers or parts. On the other hand, when you plug in a wide chip like the DS5000, you use up 2 on one side and 3 on the other side, because the chip is much wider than the divider and it covers up 3 points that can't be used later. Also as you plug in the chips, end to end, you should skip a row to allow for the overhang of the chip package past the end pins. Don't try to force two chips next to each other trying to use up the rows completely. This skipped row will be used later for something else, it won't be wasted. The next chip to plug in is the Opto isolator chip (4N35QT). Next plug in the RS-232 driver chip (MAX232CPE) Next the hex inverter chip (CD74HCT04E). Lastly, for now, the oscillator chip (SE1232). This should still leave enough rows left for the DS5000. But don't plug it in yet (if you've already got it).

You should now have 5 chips plugged in, starting at the far left of the protoboard, end to end, with the indent or dot on each to the left. The next thing is to connect GND to all the chips. Referring to the chip pinout help sheet, page 1, connect GND on all the chips to the inside power bus, on one side or the other, which ever is on the side of the chip that the GND pin is on. I won't mention it again but you need to be making jumpers, long enough to reach but not much longer, made out of #24 solid insulated wire, stripped 1/4" on each end. I usually stop and make up a dozen of the shorter ones for GND and the same number of ones a little longer for VCC. You then just "plug" in the ends to the appropriate places, sometimes using the needle nose pliers, gripping the wire just behind the bare wire and pushing it in. Don't apply any strong force to do this, they should go in without much effort. Sometimes the first time you use a tie point, it is more difficult to get the wire in than the next time you insert a wire into it. Don't use large diameter wires for jumpers, as this will loosen the tie points, and possibly cause bad connections if you ever use a smaller wire in that hole later on. All the parts I had you buy, were partly selected for their small diameter leads, where possible, to avoid this problem.

Now connect VCC to all the chips, following the same proceedure. By the way I have renumbered the chips on the DS5000 version and the DS2250 version of the schematics, to reflect the order that we placed the chips on the protoboard. This should make locating the chips physically verses the schematic, much easier. So download the new schematics,(sorry for the inconvenience) and throw the old ones (if you had downloaded them previously) away. Make sure that you throw the old ones away so that you don't accidently use them instead. On the new ones, the chip in the upper far left corner is U5 not U1. The references to these schematics in the previous lesson will also get the new versions. The old ones have been removed.

From now on we will be referring to the schematic on a regular basis. I apologize for the size of the schematic, with print that is difficult to read because it's so small, but I had to get a lot on one 8-1/2" X 11" sheet. I could have divided it up into several sheets, but following circuits across multiple sheets is more difficult than being able to see the whole schematic at once. Also, don't be daunted by the apparent complexity of the schematic, the various parts with their connecting lines running all over the place. We will cover all of it, a little at a time, and at some point later you will look at this print and think, "Gee, I understand all this". I bought a cheap pair of "Ben Franklins" (reading glasses) to use while working with all this small stuff. They help not only in reading this print, but also seeing what you are doing when trying to solder to small parts. I am 49 and my eyesight is not what it was when I was 30. It'll happen to you too, some day, all of a sudden like. Plus using a pair of these glasses, even if you don't have to, eases eye strain, when working over extended periods of time. They are cheap and are well worth the investment. Ignore the laughter that might be expressed by others when they see you wearing a pair of these, and just chalk it up to their ignorance!

About the schematic. You will notice the names GND and VCC seemingly just hanging out at the end of lines, not going anywhere. This is a standard notation for schematics. Anywhere you see GND, it is electrically connected to every other GND as if there was a wire drawn on the schematic, connecting them all together. You actually do connect them all together when you plug one end of a part or a jumper into one of the GND busses. Since the GND busses are all tied together, so too are the parts or jumpers plugged into them. The same is true for all the points maked VCC. By doing it this way, the drawing is much less clutterd with all these interconnecting lines not shown.

We are going to wait until the next lesson to plug in the DS5000. As you well know, this is an expensive chip, too expensive to buy a second because you destroyed the first, by accident of course. For now, we will do some experiments with the cheaper parts to get you used to making interconnections on the protoboard, so that when you do plug in the microcontroller, you'll get it right the first time. Just keep it in its protective package and fight off the desire to plug it in with the rest, I know you want to.

Now double check all your VCC and GND power connections to each chip again before we turn on the power. I can't say this enough times. These have to be right before you power up the protoboard. This is the one mistake that can destroy more chips than you can afford. If you get these backwards, Lord forbid, you will most certainly destroy that chip. Take the time to make sure you've got it right. Have a friend or relative double check you if you can. There will be plenty of time to play later on. There's no magic to it, no hidden grimlins. Just use the help files I provided in the previous lesson and verify that you've connected the right pins to each power bus.

If you're satisfied with the power connections, we can add some parts now. First, we need to place one of the 22UF caps at the point that the wires from the power supply plug into the protoboard. Hopefully you plugged the wires into one side of the protoboard, one into each bus, the red into the VCC bus and the black into the GND bus. The next holes were probably used to jumper the busses on each side of the protoboard together. These caps have a stripe down one side, that lines up, more or less, with one of the leads. This is the + lead of the cap. Plug this cap into the next available holes on the bus, with the + lead plugged into VCC and the other lead into GND. As we progress further into this I will quit harping on getting the parts plugged in correctly and assume the lesson has been learned. While I, in a previous disertation, referred to micros as Tinker Toys, these toys are much less forgiving of misplaced connections that a wooden Tinker Toy is. So always connect them with perseverience, dedication, and an unswerving attention to polarity (+ and -).

Resistor Color Code

Most resistors are marked with colored bands, that indicate their value, to those who can read them. Here are the colors and what each means.

       1st band    2nd Band      3rd Band         4th Band

BLACK    0      .      0      X     10
BROWN    1      .      1      X     100
RED      2      .      2      X     1000
ORANGE   3      .      3      X     10,000
YELLOW   4      .      4      X     100,000
GREEN    5      .      5      X    1,000,000
BLUE     6      .      6      X    10,000,000
VIOLET   7      .      7      X    100,000,000
GREY     8      .      8      X   1,000,000,000
WHITE    9      .      9      X  10,000,000,000

SILVER                        X       .01             10%
GOLD                          X       .1               5%

So to try this out, if we had a resistor that had the colors: orange, orange, brown, gold this is the way that you would interpret the value. The first 2 bands indicate a 2 digit number with a fixed decimal point between them. So the first two bands would be equal to 3.3 . The third band is a multiplier. In this case we would multiply by 100. So we would have the value 3.3 times 100 or 330 ohms. Another example is:  brown, black, orange, gold . This would represent 1.0 times 10,000, or 10K ohms. The 4th gold band means the value could vary + or - 5% of the total value. So a 10K resistor could be plus or minus 500 ohms.

Place another cap on the opposite end of the bus on the other side of the protoboard. The reason for these caps are to help eliminate noise in the VCC busses. They don't show up on the schematic, but are necessary. Now we are going to make a logic probe out of one of the 6 gates in the hex inverter chip. You will need a 330 ohm resistor and one of the LED's. Put one lead of the resistor into the tie strip connected to pin 10 of the 74HCT04 (U4) chip. Plug the other end into an unused strip near the chip, like one of the rows we skipped as we plugged in the chips. Now plug the shorter end of the LED into this same strip, with the longer end plugged into VCC. Make a jumper, a foot long, one that will reach to any place on either protoboard, and plug one end into pin 11 of U4. The free end of this jumper is now the working end of our logic probe.

The way this probe will work is that if there is a '1' on the input, the LED will be lit. If there is a '0', the LED will not be lit. Also, an open appears to the probe the same as a '1'. So if your confident of your connections, turn on the power. The LED should lite up immediately, indicating a '1', or an open in this case. If it dosen't, turn off power and check your connections again. Now plug the probe into GND and notice that the LED goes out. GND is the same as a '0'. Plug the probe into VCC. The LED is lit. VCC is the same as a '1'. You have just installed R2 and D1and used the gate U4E. I hope you see that the way we wired up these parts matches exactly the schematic.

Now let's connect U4A,B,C,&D along with R1 and C1and SW1 and SW2. All of these parts are in the upper left quadrant of the print. First install R1 and C1. You'll notice that one side of the cap goes to GND and one side of the resistor goes to VCC. You'll also notice that one side of the cap is marked + on the schematic. This is another one of the 22UF caps. You'll notice that the UF dosen't appear next to the 22 on the schematic. That is because all of the caps are assumed to be in microfarads (UF) unless otherwise noted. This saves having to write UF beside each one, cluttering up the print with needless text. Also the word OHM does not appear beside any of the resistors, for the same reason. All the resistors are assumed to be in OHMS. The K means 1000, so a 10K is a 10,000 OHM resistor (brown-black-orange).

What you should end up with is the - side of C1 plugged into GND, the other side plugged into the strip for pin 1 of U4. Then one side of R1 plugged into VCC and the other plugged into the strip for U4 pin 1. Remember the chips are numbered from left to right, 1 through 5, the way we plugged them into the protoboard. Now jumper from U4 pin 2 to U4 pin 3. Jumper U4 pin 6 to U4 pin 9. Then U4 pin 8 to U4 pin 5. Now take the green wire from the left switch (SW1,the one you marked LOAD/RUN) and plug it into U4 pin 1. Plug the black wire from the same switch into GND. The red wire from this switch won't be used at all. Now take the green wire from the right switch (SW2, the one you marked BREAK/NORMAL and plug it into GND. Plug the red wire into U4 pin 5 and the black wire into U4 pin 9. Flip both switches so the handles are pointing to the right (toward the side that has the ends of the leads of the switches. This puts both switches in the positions shown on the schematic, or the "Normal Run" positions. This is the position that you would have the switches to allow the micro to be running normally. Double check all your connections, until you are satisfied you have them right.

With your safety glasses on, turn on the power, and the Probe LED should lite (this assumes that the end of the probe is not plugged into anything). Plug the probe into U4 pin 2 and the LED should go out. Now flip the left switch (LOAD/RUN) to the left (LOAD), the LED should lite. Move the probe to U4 pin 4, the LED should be out. Now flip the left switch (LOAD/RUN) to the right (RUN), and the LED should lite. Move the probe to U4 pin 6. The LED should be lit. Flip the right switch (BREAK/NORMAL) to the left (BREAK) and the LED should go out. Move the probe to U4 pin 8. The LED should be lit. Flip the right switch (BREAK/NORMAL) to the right (NORMAL) and the LED should go out.

If all this worked as I described it to you, you have wired up, correctly, all the parts, so far. Congradulations! You've taken a giant step from darkness, toward the light. You should study the schematic, looking at the parts we've been working with, until you see and understand that what I had you connect up, was done just like the schematic shows. The main thing to understand is that the schematic shows the electrical connections but not the physical connections. In other words the schematic doesn't show the tie strips or the jumpers that we used in the connection process, just the fact that connections are made, and from where to where. The another thing to get out of this lesson (there were lots of "things") is the way the tie points work. There are always 5 tie points in each tie strip. If you use a strip to connect two parts together, like R2 and D1 for the logic probe, that tie strip can't be used for connecting two more parts together, even though there seems to be some left over holes in it. The strip connects all five points together, whether you use all of them or not. When we get done wiring up the complete schematic, there will be lots of unused points or holes that we won't be able to use for anything else. They'll remain unused for the duration. Thats the nature of a protoboard.

This lesson was LLLLOOOONNNNGGGG!!!!! I hope you made it through it. I listed some parts that we didn't get to in this lesson, but I wanted you to have them so that we could plug them into the protoboard and get the chip numbering scheme started. None of them were very expensive and we will finish connecting them in the next lesson. You've learned, hopefully, how to solder, read the resistor color code, learned the pinout of a serial connector, how to strip, twist and tin a stranded wire, read a schematic, identify parts, and use the protoboard and a logic probe! Whew!! That's quite a lot for one lesson!

For people who have had some electronics experience, I spent too much time explaining how to do things. For those who have had no experience, I probably didn't spend enough time. In the following lessons we will continue to connect and test more of the complete schematic, until, like I said earlier in this lesson, you will look at the schematic and the seeming "rats nest" mounted on the wooden board, and say to yourself, "It's done, I think I understand it, and I did it all myself!!".

By the way, as I finish typing this, I look over to my right and my eyes fall to rest on my wooden board with it's associated "rats nest", and on the 20 character by 4 line LCD display is showing the time, with the seconds ticking merrily by, the date, the temperature in the room I'm setting in, the temperature outside the window next to me, the relative amout of light falling on the solar cell that's laying on the board, two volt meters, one that reads 0 to 5 volts DC and the other that reads 0 to 25.5 volts DC, and the last command I sent with my X-10 remote over the power lines in my house, all the while, every 30 seconds, a light in the next room is turning on and off, commanded by the micro. In other words, all the software we are going to be using to complete this course is written, tested, debugged, and running now, on my rats nest.

The rest of the lessons in this course should be comming at the rate of at least one a week, until we finish the course. Things come up, and I have a regular job that pays the bills, that I have to spend at least 40 hours a week at, so don't hold me to this schedule, but that's what I'm shooting for. So hang on!! It's going to be fast and furious.

My home page is .

On to lesson 13.