Make: Electronics... a book review and BLOG

[The Chairman]

Experiment 15: Burglar alarm revisited...

I guess I was expecting too much, or expecting it too quickly as I was slightly disappointed in this experiment. Essentially, we took an P2N2222 a transistor and used it to switch a relay. Then we latched the relay. Then we used the relay to switch experiment #11, a modular experiment (high/low alarm), on and off. FWIW, I can barely hear this alarm. Yes, it has a nice high/low oscillation but it's not particularly audible. I reduced the resistor considerably and it's still faint. The last half of the experiment is soldering the entire mess together and mounting it in an enclosure. Sorry, but I'm not going to mount a fairly useless circuit in an enclosure, even for the experience of it. I'll wait until I have something worth my while.

It was cool to see how far I've come with being comfortable with LEDs. It allowed me to work ahead of the reading and experiment a bit The plans called to replace the LED in the transistor circuit with the relay and then power the alarm. I let the relay power LEDs instead. Green for closed and red for open. I was also surprised to find that the window switch that came with the kit was labeled wrong. NC was NO and vice versa. I wired in an On-Off-On SPDT switch to give the circuit on/off/test modes. I also installed a diode in the circuit to protect the transistor as it seemed a good idea. However, during my reading, it became apparent that I put the diode in the wrong place where it was protecting the relay rather than the transistor. No harm was done to the relay and it was easy enough to move on the breadboard.

The next section will introduce the 74xx series of logic ICs. I'm kind of surprised that we haven't done more with power, rectification and using capacitors to even things out. No mention of voltage regulators either to further smooth things out. Yeah, they're just a Google search away but I was hoping for a more logical approach. That being said, there are a number of YouTube videos that are worth watching. There was one on the PUT that went into a more lucid detail about how they work and what to use them for. I also stumbled upon some tutorials about 555 timers used in oscillator circuits. :





Yeah, I know I'm jumping ahead with this, but that's the joy of independent study. If it interests me, I want to see it.

 

[The Chairman]

Caveat... or some lessons are best learned twice.

About their alarm circuit. On the first introductions to transistors, I realized that the pin out of the P2N222a transistor in the book didn't match the actual pin out on the ones that came in the Radio Shack kit. I even went online and found that it could either be CBE or EBC depending on the manufacturer. Reversing the pins caused their circuit to work. Kewl. As I was assembling the circuit in post 11, it didn't seem to work at first. I examined the circuit and remembered the reverse pin out for the transistor. That made it work and I thought to myself that this would bite me at least one time more. So, right after I was wrote about not being able to hear the sound from the speaker, the post lady delivered my package from Jameco Electronics. They had mentioned that the speaker size could be an issue, so I got a six inch speaker. I signed for the package and while I was down there I quickly soldered two leads to the speaker (red for positive and black for negative) and plugged it in. It's still barely audible. It was at that time I spotted the 2 P2n2222a transistors in the circuit. Flip and flip and the circuit now makes a whole lot more noise. No, not near enough noise to frighten a burglar, but enough to let you know you've tripped the alarm. I like the fact that I made this circuit work and it was a very simple fix.

Green light is on, the intrusion alarm is armed.

Red light means the intrusion alarm has been tripped!

WOW! The circuit is so loud, if you get real close, you can hear it through the .jpg! :shocked2: :shocked2: :shocked2:

 

[The Chairman]

Experiment 16: Making a Pulse.

I usually do the experiment and then write about it, but today is different. While I was in the Grotto last night sussing out the issues with the intrusion alarm, I couldn't help starting to delve into the next experiment. What would you know: it's all about 555 Timers. I hadn't realized that when I posted the youtube videos earlier. I was first introduced to 555 and 556 timers sometime in the nineties. No, i never got the chance to play with them. I was too busy fixing automobiles, learning about PCs, Networks and raising a family. They really intrigued me and I could see how they would be more than useful. I think there's even a 555 Timer Cookbook stashed somewhere in my library. So finally, I get to play with them. since I was down here already resolving issues with the earlier circuits, I took a few more moments to play. After all, I was pretty psyched about getting the circuit to scream a bit.

That's when it hit me. So far, the Make: Electronics book has been more than adequate and even a bit of fun. Sure there have been some momentary failures, but perseverance and luck turned those into learning moments. But the one thing I dislike about the book is the departure from using schematics above all else. Look at what I am working from:

I find the way he set this up to be as counter intuitive as it is blurry. Up to now, he's had positive on the left, but that's no biggee. He just doesn't seem to like schematics and I think it puts his students at a potential disadvantage in the long run. First it oversimplifies the circuit, so I really don't have to understand what's happening in it. That's fine if I was just trying to "pass" with the least amount of effort. I'm reading this book to get a fuller understanding. Yes, his explanations are clear and I have understood the concepts to this point and will probably continue to understand them, but I LIKE schematics. I made my living off of being able to suss out a car's wiring problems for thirty years. It's a skill that most newbie and even a lot of oldie mechanics seem to lack. Here's a pic of my breadboard where I left off last night.

Notice how I have the power strips connected. This makes it easy to run things intelligently. R5 is being run from the left side positive strip rather than over everything. The jumper from the left negative strip to just under pin 5 has been rerouted from the right side. I think it makes for a neater board and makes me think a bit more.

BTW, since I brought my laptop down here, I spent a few minutes cleaning up some space adjacent to my electronics bench for it to sit. I moved the anvil down near the benchtop drill press. It's days are numbered as I need a bigger floor mounted drill press. I'm always having to finagle things around in order to drill them.

 

[They call me Tater]

Haha brings back memories....Enjoy! Unfortunately other than old stero gear most of the cool stuff is SMT these days.

 

[ams511]

That's the exact point of failure.

After numerous brainstorming sessions, we (me and the 2 kids) failed to put together a sales pitch to convince the wife we have good reasons to hang a 6 meters antenna dangling across the living room.

Project written off.

Where we lived at the time my room had access to a porch on the second floor. My father ran the wire out there and then under the door to the radio. So I was lucky and had an outdoor antenna.

 

[The Chairman]

When I first put the mono-stable timer circuit together yesterday morning I figured it had to be some sort of logic circuit. It was easy enough to assemble even though I was not using his exact routing. To say the least, I was surprised when I hit either S1 or S2 that nothing happened. Nothing happened again when I hit them simultaneously. I checked over my circuit and rechecked the values, but it looked just fine. Since I had a couple of other projects screaming for my attention, I left it mellow until late this morning.

My first move as I sat down at my electronics bench was to waste time. My Kindle was set to a novel I was reading at breakfast, so I continued to read. All the while, the unrepentant circuit sat there and mocked me. I could feel it sending empathic messages suggesting that I would never be able to master this timer after all. ARRRGH! Finally, I turned my attention back to it and ran through all the button pressing I had done yesterday. Image that. Nothing was accomplished yet once more. I believe that circuits, like PCs are best played with before you try to fathom their eccentricities. Push buttons and twist knobs and see what you can produce without reading the directions. It was obvious that I had not adjusted the pot, so that was next. I cranked it all the way to the fight. Nothing happened yet again. I cranked it to the very middle where you can feel the detent ever so slightly. Nada. I cranked it all the way to the left. Whoa! The LED came on when I hit S1. It went off when I hit S2. I cranked the pot to the right a bit at a time until pressing S1 wouldn't work. That was connected to pin 2 of the timer, so I plugged in my DVOM to see what was happening. I had just over 6V until I hit the switch. It dropped to just under 3V. I also noticed that I didn't have to hit S2. After about seven seconds, it blinked off automagically. I was getting 0V at pin 3 before I hit S1 and then it popped up to 7.9V I played a while longer and then started reading the explanation. Since I had watched the youtube videos, I thought I would have this down, but I was confused about what was happening almost until the end. None of the youtube videos had suggested that there were two comparators embedded in the 555. The circuit flipped when the trigger went below 1/3 of the circuit voltage (9V). It then flops when pin 6 hits 2/3 of the circuit voltage. Pin 4 is a simple reset button that sets the timer back to normalcy. Kewl. The additional information of the comparators really helped me to visualize this chip.

It's really hard to comprehend the impact this chip has had on our society. Tens of billions of the 555 and the 556 timer chips have been sold with very little change since it's inception making it the most popular chip of all time. My next step is #17: Set Your Tone. I see that it requires an additional 555 timer and it should be fun like this one was.

 

[The Chairman]

Make: Electronics Experiment 17: Set your tone...

OK, this was the most complex experiment thus far. The book said it would speed up with less hand holding at the beginning of chapter 16 and they did not disappoint. You have to pay attention to what you are reading as well as to what you are doing. One careless slip, like reversing the polarity on my breadboard can have peculiar results. My troubleshooting nature had to come into play because of such a slip.

First, I couldn't find the prescribed 0.047 uF capacitor. I put everything together as it was supposed to go together, but I couldn't for the life of me figure out which capacitor to use. Like most conundrums, I resorted to Google. Everyone wanted to sell me a cap, not explain them. There was one page that kinda sorta helped, but it left me confused. Then I resorted to Wikipedia and if I understood the calculus, I might have been able to wade through it. Back to Google. I got that for most three digit caps, that the first two were the significant digits and the third was the number of zeroes from pF. I didn't understand how 104 (an example used) was 0.1 uF. I figured it to be 100 uF. What was I missing? So, I went ahead and bought the Kindle version of the Encyclopedia of Electronic Components by the same author. Zipping right to the Capacitor section, I read the longish, thorough yet understandable section on capacitors, and then (like the ball thrown in my direction) it hit me; Nano Farads! uF>nF>pF. Each of them an order of a thousand difference from the one above or below it. Unfortunately, the USA doesn't like to use nF. We stick to uF or pF. Now, that's OK, and it was simply a mental lapse on my part. With that finally understood, I saw that 0.047uF= 47nF= 47000pF. I was looking for a 473 (a 47 followed by 3 zeros). Nope. Not here. I had some other button caps, but they were really weirdly marked. I went to Radio Shack and spent $3 on two 0.47uF caps. I could probably buy a hundred on e-bay for that price or close to it, but I'm leaving for Curacao on Monday and wanted to finish this section.

So, I plug in the right cap, plug in the power supply and RRRRRRRRRRRRRRRRRRRRRRRRRRR... the resultant tone is music to my ears. The rest of the experiment was making a dual tone buzzer like experiment 11, but we're using 555 timers instead of the PUTs. It was good to see everything work, and I am even understanding the underlying physics and logic of what's happening. At one point the book wants me to combine the circuit from 16 so I have the tone for just 5 seconds. The hookup is easy. remove the resistor and LED from pin 3 on the pulse circuit's 555 and connect it to pin 8 on the tone circuit's 555 with a simple jumper. I also had to remove the other positive feed to pin 8 on the tone circuit's 555.

Nothing.
Nada.
and Squat.

Really? I quickly removed the jumper and installed the LED and resistor. The pulse section is working. I try the tone circuit by itself and see that it works just fine as well. However, when I put them together I get NN&S. Again. So, here's an opportunity to do more trouble shooting. I mean, if you're going to try and find a positive to something not working, that's as good as anything. My first tool of choice was my logic probe. High/low tones tell me what I am getting at each location. Something's not right, but I can't really quantify it. Everything on the logic probe looks kosher. Next I resort to my antique digital DVOM. I have soldered in some of the breadboard jumpers to banana clips that work as leads for my DVOM. That way I don't have to hold probes while I trigger something. Ah. When I plug the output pin #3 from the pulse circuit it gives me 7.6V with the LED/Resistor plugged in, but with the load of the tone circuit, it drops down to just under 3V. The 555 requires 5V to operate, so I pop in another 555 timer into the pulse circuit and BINGO! I get the tone for 5-6 seconds and then off. I'm getting 7.67V even with the tone circuit drawing a load. I had correctly determined that the 555 was faulty. Before I threw it away, I hacked it apart to see what was inside. Wow. It's mostly plastic. I got to the circuit, but I can't see it very well using my magnifiers. You would need a microscope to view this. I wonder how it compares to 555 timers from the 70's?

The problem with the logic probe was one of scale. It gave me a high tone when I pushed the pulse circuit's switch. I don't see a setting on this logic probe to set the minimum for "high". Kinda sucks.

OK, it's Sunday and I'm leaving tomorrow afternoon for Curacao. While my Kindle will be on the flight, none of the other electronics paraphernalia will be. I'll try to pick this up in a week or so. This has been a fun learning experience for me and I suspect that a number of you would have just as much fun as I am. I think it's important to keep learning as much as you can so that you exercise that muscle lying between your ears. I'm just a bit over half now and the next experiment utilizes 555 timers to build a reaction timer. It's time to turn off all power to the electronics bench and go pack. Tchuss!

 

[fjpatrum]

Excellent post(s), Pete. Looks like this primer is basically a 100 level intro lab class. Quite fun. I'm using the reed switches like your window "sensor" for my video lights. Once I get a gasket/o-ring that keeps water out of my housing I might actually get to test the unit under water.

 

[The Chairman]

Thanks fj! I've never taken a formal class, so I have no idea how thorough this is compared to Electronics 101.

ywfWDtKfieo

 

[The Chairman]

Make Electronics: Experiment 18: Make a Reaction Timer.

OK, I assumed that this nest section was just another adaptation on the 555 Timer. It's not. Yes, it uses a 555 Timer and it will introduce us to the bistable (flip flop) circuit, but it's really about digital displays and using a 4026 decade counter/decoder. I went to DJ's for breakfast this morning, still fairly stoked about our trip to Curacao. Yes, I've got lots of writing to do on that as well, but it's been over a week since I hit the Electronics Bench and I was worried that I might lose the momentum. While I usually read a novel at breakfast on my Kindle, I chose to read Experiment 18 instead. It was intense on one level, but fully and easily comprehensible on all the others. I found that I really wanted to get to the bench, so I ate quickly and hurried on back.

I had taken the time to study the pin-outs of the Digital Display as well as the 4026 chip while at breakfast. The notes suggested that I use a breadboard with at least 63 rows and so I prepared it, connecting the positive and negative columns across the board and cleaning up a bit before I got started. I put in the Display with three resistors and manually checked all the LED segments. Each segment is noted with a leter, starting from the top element, a, and going around clockwise with the middle segment getting g. I put power to sequential pins to test each segment, first on the bottom and then on the top. After I finished, I realized I hadn't seen 3g light up. I went over the top pins a few more times. 1g lit, 2g lit but nothing from 3g. Well. isn't that odd? I might have a defective Display. A quick check of the pin-out schematic shows that 3g comes out at pin 12 on the bottom row of pins. Yep, it works too.

I made a comment earlier how I wished the author had stuck with schematics rather than giving us a physical layout of the breadboard. Well, he's starting to do that more and more and he's also modifying that with giving the pin number of the Display. Digital circuit pins can play with your mind. If you look from the top of the IC, #1 is on the top left and sequence goes CCW. Look at the chip from the pin side, and #1 is on the upper right and numbers sequence in a CW direction. Clear as mud right? A schematic showing all these connections would be uber confusing. So, the author wrote the Display's pin number on the 4026 Chip's legs. I was using jumper wires for this, so it worked out perfect. It was easier to accomplish and made understanding of what you were doing rather intuitive. Good Job. Here's a pic after wiring in the first IC to the Display:

OK, that was simple enough, so I continued the experiment and added the other two 4022 CMOS. It was simple enough to do after the first one. Here are some pics

The next step was adding a 555 Timer in order to drive the counting process. Here's a video: I'm not done with this experiment yet, but I'm done for the day.