Monday, September 29, 2014

Experiment 16 Part 1 (Chapter 16) -- Invasion of the Wires!

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.

Wednesday, September 17, 2014

Experiment 15 (Chapter 15) -- Pure Logic

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):

Friday, September 12, 2014

Experiment 14 (Chapter 14) -- The Joy of Wiring!

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.

Video below, along with some additional photos: