I'm almost done with Experiment 16, but will need another day or so to finish it. In the meantime, I wanted to share some photos of the process of wiring this monster up. Charles always does a great job of keeping his wiring clean and presentable. Me? Not so much. I should probably invest the time (or money) in some of the small pre-bent connector wires that take less space on a breadboard. But not today.
I've got a HUGE box of jumper wire and I'm determined to get my money's worth from it! As you can see in the photos below, I did have a method to my madness. After inserting the five chips, I began with wiring up the 5V and GND connections. Red wires on the right, black wires to the left.
After that, I used colors for each of the buttons -- orange for A0, green for A1, yellow for B0, and blue for B1. White wires were used to make connections between leads on the chips. Even with the colors, it's a mess. Sorry.
Up next is the LEDs, resistors (220ohm) and testing. Do I expect it to work right on the first try? I hope so! I was pretty careful about checking my wiring, and using the colored wires for each button helped me keep track of all the connections. That said, it's a lot of wires, and I'm sure my tired eyes missed a connection or two. I'll work on that later today and hopefully post the results tomorrow.
I have always enjoyed building circuits with logic chips. I took a class 20+ years ago in college that had us optimizing logic circuits -- I both hated and loved that class. I loved the mental exercise of it... I hated the fact my grade depended upon successful reductions of large circuits. This stuff comes a little easier to me than other aspects of electronics, and I really enjoyed reading Chapter 15 and revisiting logic chips and wiring up this simple little circuit.
I've read ahead four or five chapters, so I know what's coming... I tell you this so you'll just pay attention to what you read in Chapter 15 and don't worry about modifying the circuit. You'll have plenty of chances ahead to improve this circuit and learn about reducing the number of chips you need. It's good stuff and as long as you examine and understand Charles' method for showing open/closed and 1/0 input and outputs... you shouldn't find Experiment 15 too troublesome.
If I had any issues with this circuit, it was dealing with these annoying little pushbuttons and the proper orientation for inserting into the breadboard. Insert them the wrong way, and they're basically always on (Closed or Pushed) and the LED stays lit. Once I figured out what was going on, I turned the buttons 90 degrees and everything was fine. (I used my multimeter and the continuity setting to check how the buttons worked and to verify I had the orientation wrong.)
As you can see from the photo, I'm once again back to 5V DC regulated. I used my meter to verify the voltage on the rails of the breadboard before moving forward with the experiment -- don't risk burning out your chips by applying to much voltage.
The video below pretty much speaks for itself and shows you how the circuit works (and how a player could cheat):
First, I'd like to say for anyone following along that I'm sorry for the delay in getting a new experiment posted. I'm teaching an after-school science project club at my sons' school and have spent the last few weeks getting equipment, supplies, and instructions together along with fine-tuning the projects. The club has kicked off and is going fine, and things have calmed down a bit... now I can get back to Make: More Electronics.
Experiment 14. Wow. A good project to really dive into and think about what's happening in the circuit, but also... a lot of wiring! You're going to really want to pay attention and double and triple-check all your work. I thought for certain I'd done everything right after a double-check, but after applying power it still wouldn't work properly... no amplification and no LED lighting up. Another check was done and sure enough... I'd made a bad connection on one of the 555 chips. Finally, success... but more on that in a minute.
I wanted to share a bunch of photo with this experiment that detailed my building of this circuit. The reason I did this was not only to point out a few key differences between the layout of the components on my breadboard and Charles' breadboard, but also to talk about how I go about assembling a circuit. I don't always follow this method... but most of the time it works for me.
First, I inserted all the chips, LEDs, and the electret. Based on the schematic, I guessed at the best spacing of the components. Charles managed to get the entire circuit on half of his breadboard, but I spread it out over the entire breadboard. If I wanted to transition this circuit to a perfboard for a more permanent boxed project, I'd probably continue to close up my circuit and reduce the spacing and such. I did cut almost all of the leads of the resistors, but not the capacitors because I have a limited quantity and I never know where I wish those leads to stretch.
After placing the first wave of components, I took an inventory of the resistors in the circuit (including the 1M variable resistor). I keep all my resistors in little baggies and I really only want to pull them out one time. Therefore, when I pulled out the 1K back, for example, I pulled out three of them and clipped and placed them as necessary. A few times I realized I would need to move or relocate a resistor, but it was rare.
Speaking of resistors, take a look at Figure 14-1 that holds the schematics for Experiment 14. Look carefully where the 1M variable resistor (pot) is located and how it wires into the LM741. Now look at Figure 14-3 that shows Charles' wiring. Notice anything different? Yep -- he's flipped his pot upside down... the tip-off is that brown wire running from the top lead to Pin 2 on the LM741. Notice the green wire running from the bottom lead (on the pot) to Pin 6 on the chip? Not a big deal, but if you try to wire up your pot to match the schematic, don't try to compare your final result to Figure 14-3. I was trying to figure out what was so strange about the pot, and then I realized it the middle pin was jumpered to the top pin (in Figure 14-3) with a teeny-tiny brown wire. Look close... it's there. Again... not a big deal. I wired it up my way and got the circuit working. But just be careful. Charles wires up things in a very efficient manner that also lends itself to photographing the final circuit. Because of this, you'll occasionally find workarounds that he uses that don't match exactly to his schematic.
Sometimes, however, you've got to come up with your own workarounds. Example? In the schematic, each of the 555 chips has a single 150k resistor coming on Pin 8. I didn't have any 150k resistors, but I did have 100k and 47k resistors. If you look at a close-up photo I took, I just used a 47k as a jumper to connect Pin 7 to Pin 6. The 100k jumps Pin 8 to 7... and 47k jumps Pin 7 to Pin 6. And then a small capacitor makes the final connection to Ground. If you look at Charles' circuit in Figure 14-3, you'll see his solution which is much more elegant and clean. I didn't have 150ks, so I had to improvise. Pin 7 to Pin 6 has to be jumpered anyway, and that 47k will be felt whether it's part of a 150k single resistor or a two resistors in series as I've done.
Testing continued to be a slight problem for me as I've never been able to get good results from these electrets. I probably should have purchased some new ones, but I got enough valid results from the circuit to understand what was happening. (Of course, I got a finger burned good by using the wrong speaker... won't make that mistake again.)
Below is the video of my test. As you'll see, the electret picked up the scraping of the pin and the input was amplified with the speaker. But once I stopped the input, the circuit began to cycle for some reason. I've played around with it a bit more to see if I can figure out how to break that loop, but no solution yet. These sound circuits have been fun, but I'm really ready to keep moving forward and see what comes next. I've already read the next few chapters, and I've always enjoyed working with logic chips... so I'm looking forward to the next handful of builds.
I'm going to wrap up Chapter 13 with a couple of videos and some photos. Unfortunately, one of the videos you might be expecting is NOT here. I synched my phone and downloaded photos and videos, but the video for the circuit shown in Figure 13-7 (page 96) has disappeared. Poof. It's frustrating because although it wasn't a tricky circuit to wire up, it did take some time. My wiring wasn't as pretty as Charles' (no big surprise), but the circuit did work -- a suitable level of volume (tapping on the electret) got the 555 timer chip started and the 3" loudspeaker to making an awful noise. It would definitely make someone stop talking loud, but I'd probably prefer a higher voice volume than the pitch coming out of that speaker.
Where are you, video!??
Here's a photo of the missing video's circuit. I didn't vary much from Charles' diagram with but a few exceptions -- instead of the 33K (near the bottom of the schematic) I used a 47K... no 33K in my batch and I didn't feel it would be detrimental to the circuit to avoid putting two 15Ks in series. Also, I didn't have a 0.068microfarad capacitor, so I substituted a 0.1microfarad. Again, the circuit worked, so these substitutions didn't seem to have a negative effect.
You can't see the speaker, but you can see the two wires exiting the bottom of the breadboard... it's about a three foot length of wire. Lots of popping and static, but it worked.
Note to self: Find a small baggie of mixed capacitors in all values and buy it! I have a good assortment, but I continue to find values I don't have in my capacitor collection.
After completing the larger circuit, I went back a few pages to a small experiment Charles described that uses two 2N2222 transistors and a handful of 1K and 10K resistors. Depending on the wiring of these resistors, you'll gain a better understanding of the subject of Emitter Follower that Charles introduces on page 94. Voltage at the Emitter (E) is directly related to the voltage at the Base (B). It took me a few reads and then performing the experiment with a meter to grasp what was happening, but it does follow the most basic understanding of a 2N2222... and it pulls in the concept of voltage division once again. Very cool!
Note: You can perform these experiments with a single 2N2222 but it goes faster if you have a pair. Even better, if you have four 2N2222s, wire them up following Figures 13-5 and 13-6 and knock all four tests out on one breadboard.
The chapter does round out with a discussion on some of the problems that Charles encountered with his circuit. I was providing a solid 9V using an AC Adapter with a selector for voltage... whereas it appears that Charles was using a 9V battery more often. Some of the technical issues he encountered seem to be related to that fact. If you're using a 9V battery, definitely read some of the suggestions (on page 98) for fixing the circuit if you're having issues with it.
Up next? Experiment 14! Videos below... Part 1 at top, Part 2 on bottom.
My apologies for delays in getting new posts up, but I've had a few work-related items drop in my lap as well as a special project come up where I couldn't say no. I write non-fiction (technology) books for a living, and part of that requires me to create proposals for new books. I'm "down" right now -- meaning I have no books to write. I usually try to be finishing a book as I'm starting a new one, but that doesn't always work out. Last week I was working on a new book proposal that required a LOT of my time...
The other item that stole my time last week was a chance to assemble a laser cutter. Two, actually. I traveled to my parents' house to meet a good friend of mine, Patrick Hood-Daniel. Patrick owns BuildYourCNC.com, where he sells DIY CNC machines, 3D printers, and... laser cutters. Patrick and I wrote a book together years ago called Build Your Own CNC Machine and then followed it up with a Build Your Own 3D Printer book. Patrick has since designed a new laser cutter called BlackTooth, and he came to Florida to help my dad and I each build our own laser cutter. It was a good learning experience as well as a great time to catch up and visit.
Building a laser cutter was definitely interesting. The shell of the laser cutter is made of MDO (medium density overlay), and while it looks like wood, it's resistant to moisture and it resists burning (flare-ups after the material is cut by the laser are unlikely to set it on fire). This is a 40W, so not super powerful -- it can cut 1/4" plywood but slowly. It's got an exhaust fan where I'll be able to vent the fumes from cutting plastics/acrylics. A water pump circulates water to cool the laser and a small air pump blows air out at the point of the cut to further help prevent flare-ups. This one works like a CNC machine, with two motors controlling X and Y axes... there is no Z axis, however, since the laser controls depth of cut by modifying the power to the laser as well as the time the laser is turned on.
Wiring it up was tricky... and not tricky. It follows a fairly straight forward path, with a power supply providing power to both motors and the laser as well as the fan and water and air pumps. Tubes and wires have to be carefully routed because you've got moving parts inside, and that's where Patrick's help was invaluable. A lot of people have built this laser cutter all on their own, but I have to admit it was nice having the designer there to double-check everything.
Anywa... I'm back in Atlanta now, so I'll be trying to catch up this week on some new posts now that I've got the proposal completed AND the laser cutters assembled.
I'm breaking Experiment 13 into parts... and there's no video for this first part, sorry to say. The first half of this experiment involved replacing some of the components in the Experiment 12 circuit, namely the 100K resistor with a 1M potentiometer and the 10k pot with a flat 10k resistor. I left the 10k pot in and just cranked it to its maximum value (and checked it with my meter). The 1M pot allows for some tweaking, but I found in my experiments I had to dial it down quite a bit to the lower range (around 200-230k).
Before diving into the experiment, however, I want to address one of the goals of this chapter -- designing a circuit. Charles opens the chapter with an example description of the final circuit (an alarm will sound if the input -- your voice or other noise -- exceeds a threshold) and then proceeds to ask the question - how do you go about designing a circuit knowing the end result you desire?
The key statement IMO is "so long as a circuit can be broken down into sections, and you can make them communicate reliably with each other, and you can test them one at a time, the design process doesn't have to be too difficult."
I've built a few circuits over the past few years where I stole a piece from here and another piece from there... I wasn't designing the schematic and circuit from scratch, but instead using pre-existing circuits that I understood. And that's what's going on here... Charles is pulling bits and pieces from earlier experiments to create one final circuit... and it's pretty slick and easy to follow if you take your time.
For the first part, I just wanted to recreate the input half of the circuit -- the electret must receive input and an increase in voltage needed to be detected from the LM741 with a meter. Figure 13.1 provides four different locations in the circuit to take some readings... I'm including my results below:
These values won't mean much to you if you haven't read pages 91-93 in the book. The takeaway was to notice an increase in the input voltage reading (AC)... my tapping on the electret with a specific metal pen (voice wouldn't cut it) was providing 0.004V (40mV) and the LM741 was outputing 2.1V at Point C in the circuit (and AC voltage -- remember, the op-amp outputs AC). Point D in the circuit, however, is where the second half of the experiment will continue, and it needed to be at least 2.5V (AC) to trigger the eventual 2N2222 transistor that will be added (in Part 2 of my Experiment 12 post). I was getting 2.6... so everything is good.
One troubling part to me is the sensitivity of the electret. My voice just doesn't trigger it... even when I'm speaking right into it. Only tapping on the shell with metal pen would get me the upper voltage I needed. I had to practice a bit to get a consistent tap strength, too.
But... it works. I'm getting over 2.5V at point D in the circuit (referencing Figure 13.1) and am now ready to move on to the next half of the circuit...
Preamp and poweramp... both are found in the simple circuit for Experiment 12. I actually had an LM386 in my collection of parts, but it had a mangled pin. Thankfully this is a fairly common component, and Radio Shack sells them for $2.00... so no waiting.
The experiment does explain how to bump up the gain from the basic 20:1 to 200:1, but I'm going to stay with the default setting for now. If anyone attempts the upgrade and has a video, let me know and I'll be happy to share here with an update.
For my circuit, I did have to make just three modifications. Obtaining two matching 68k resistors was easy (for the middle voltage), but I didn't have a .68 microfarad... in goes a 105 or 1microfarad. I had to substitute a .1 for the .047 microfarad, and I took Charles' advice to add a very large capacitor between + and GND... a 1000microfarad... that helped cut the noise substantially!
I did have the 10microfarad capacitors (x2) and the 330microfarad. After adding in the electret and the 50ohm speaker, you can see my final circuit below.
Initial tests were horrible... lots of static and hissing. Only after replacing the wires to the speaker with a 3' length of braided wire did I get some great results as you'll see in the video. The troubleshooting section is valuable... if you're having static and popping, there's probably a fix.
I'm almost done with Experiment 16, but will need another day or so to finish it. In the meantime, I wanted to share some photos of the process of wiring this monster up. Charles always does a great job of keeping his wiring clean and presentable. Me? Not so much. I should probably invest the time (or money) in some of the small pre-bent connector wires that take less space on a breadboard. But not today.
