Experiment 18: More components.

A small update. Saturday I received the rest of the components that I need for the Reaction Timer (Experiment 18 of Make:Electronics) and the rest of chapter 4.  I couldn’t get all the components on the shopping list (see pg. 147) from my online supplier so I had to choose some alternative components. Notably the Panasonic latching relay (I got an Omron which shouldn’t matter) and the Kingbright LED numerical display (couldn’t get the three numerals in one package so I ordered three individual numerals). Since the book only describes the three numerals in one package I had to find the pin outs of the individual numerals that I have. A simple Google search gave me the datasheet on the Kingbright USA website (here). Unfortunately I had no I time to get started with experiment 18 because I was refurbishing our bathroom this weekend (Off topic. I discovered that the Dremel is very handy while cleaning the seams between the tiles of the bathroom).

Part of the data sheet of the Kingbright SC36-11EWA (pin out at the bottom right of the image).

Kingbright SC36-11EWA numeral LED’s.

The Omron latching relay that I received.

Valentine LED chaser part 3: problem solved

I reread the part of Make:Electronics about the inside of the 555 timer in the astable mode (page 162 of the book) hoping that this would give me a clue about what went wrong with the Valentine LED chaser. This gave me the idea that the 1uF capacitor connected to the pin 6 of the 555 timer wasn’t properly charging or discharging. After examining the circuit board I understood why. I had soldered the 10K resistor protecting the potentiometer to the wrong side of the capacitor, the negative side. Therefore the capacitator simply didn’t charge. I disconnected the resistor from the negative side of the capacitor and resoldered it to the positive side. Everything worked fine now. I’m glad the circuit works however the lay-out of the circuit could have been simpler to avoid the spaghetti of wires that I ended up with. All in all a nice deviation from the book. With everything I learned this far from Make:Electronics I was able to finish the Valentine LED chaser (Remember that I had hardly any electronic skills when I started with the book). A short video of this project can be found on this YouTube page.

Finished Valentine LED chaser.

Valentine LED chaser part 2: transfer to the perf board

Last Friday and Saturday I transfered the components to the perf board. I used regular perf board this time instead of the breadboard type perf board that I used for the alarm circuit. I had to make a sketch of the circuit on the perf board before I started to solder. The sketch was simply hand drawn and depicted all the components positioned on the perf board and all the solder joints. I realised this circuit needed a lot of soldering. The wire cutting and soldering indeed took a serious amount of time even more than anticipated. The end result looked like a spaghetti of wires (see image). I attached the 9V battery and… only one LED started glowing. Disconnecting and reconnecting the battery prompted other LED’s to glow but nothing like the LED chaser. I replaced the 555 timer and the 4017B counter. Same result. This leads to the assumption that the 555 timer isn’t properly triggering the counter. Alas no finished LED chaser for this Valentine but that doesn’t mean I’m not going to solve the problem. To be continued.

LED chaser. Just one LED glows. Probably due to the 555 timer that doesn’t properly trigger the counter.
Spaghetti of wires at the back of the perf board. I could have given the lay-out a little more thought.

Valentine LED chaser part 1: the breadboard

It is time to take a temporary departure from Make:Electronics. The question is: has all these theorie and experiments from the book enabled me to finish my own project? After working with the 555 timer in astable mode last week I remembered an article about this chip that I read a year ago, the so called LED chaser. I read the article last year on the makezine website. It’s an electronic circuit that illuminates ten LED’s in the shape of a heart (you can find the article here). With Valentine day next Saturday this could be a nice present for my wife. The circuit needs a 555 timer, a 4017B decade counter, some capacitors and resistors, a potentiometer and of course 10 red LED’s. Luckily I had all the components (I used 1.2K resistor instead of 1K and 250K potentiometer instead of 200K).  I have built the circuit on a breadboard today and it worked almost immediately. That leaves me almost a week to solder it to a board.

Print out of the schematics of the LED chaser found on Makezine.


Finished circuit on breadboard. The LED’s do not resemble the heart shape yet.

DIY bar stool as part of the bar table

A couple of weeks ago I built a bar table out of scaffolding wood. Today I had the time to build a stool of the same material. I used a drawing of Cando (a Belgium based DIY shop). You can find the link of the drawing on their website here together with the bill of material. Cando has a series of drawings of scaffolding wood furniture even of a complete outdoor kitchen (as long as you don’t mind deciphering the Dutch instructions). I got the scaffolding wood cut at the desired length at our local DIY shop. It just needed a little sanding. As with the bar table building was straight forward using 5 x 50 mm chipboard screws. I’m happy with the result. The stool is sturdy and has a nice rough look. Given the low price of the scaffolding wood it is also cheap.

Stool happily together with the bar table

Experiment 17: The astable mode of the 555 timer

Last weekend I had a chance to continue with the next experiment. Make:Electronics suggests to set it up on the same breadboard that still has experiment 16 on it. This is for later experiments when the 555 timers will be chained. Again this is an easy experiment although I almost forgot all important connection between pin 6 (threshold) to pin 2 (trigger). Instead of one pulse in the monostable mode a stream of pulses is generated. The loudspeaker that is connected to the pin 3 (output) generates a (faint) tone. According to the book it is 1,5KHz (this equals to 1500 pulses per second).

Overview of breadboard with on top experiment 16 (with led and potentiometer) and beneath it experiment 17 with the speaker on the side

Close-up of experiment 17 (bottom IC)

Experiment 16: monostable mode of the 555 chip

This experiment (and the next experiments) are centered around the 555 timer chip. The circuit that been built (figure 4.14 of Make:Electronics) results in the monostable mode of the 555 chip. Once triggered the 555 emits a single pulse of a fixed duration. I lacked the required 5K linear potentiometer and I used a 2.5K instead. I decreased the resistance of the potentiometer step by step and at a certain threshold the led that is connected to the pin 3 (output) emitted a pulse. At this time I measured a voltage on pin 2 (trigger) of 3V. This experiment is straightforward and I encountered no problem. Afterwards I changed the capacitor on pin 6 (the threshold pin) from 47uF to 22uF. The duration of the pulse halved as expected.

Overview of the circuit with the 555 in the middle and the potentiometer on the left.

Close-up of the circuit

Building an Intrusion alarm part 5 (finishing up is hard)

I spent several hours fault tracing the circuit from the intrusion alarm. I used the multimeter together with the minigrabber and checked the relay part of the circuit. I was able to measure the voltage over all the components and at first couldn’t find any problem. I decided to replace the transistor since the soldering looked a bit messy. Tried it again and nothing. Then I started applying power directly different parts of the relay circuit. I found that the first resistor (the 10K resistor in figure 3-93 of the book) had a bad connection and blocked the current. The solder joint looked messy. I cleaned it using a solder-pump and soldered it again. Problem solved.

Next I wired the external parts to the circuit board. I finished the soldering and then powered the circuit and again no click in the relay and no alarm. The led’s in the enclosure worked fine however. I took out the circuit and tested it. It works without a problem. So I’m clueless.

Nevertheless I learned a lot from this chapter and especially experiment 15. I learned to make simple circuits and mount everything in a box although I can certainly improve my skills on this. For the moment I will leave the intrusion alarm (it’s taken far too long for my taste) and continue to the next chapter (chips). Maybe I will revisit the intrusion alarm later.

Building an Intrusion alarm part 4, disaster strucks.

I completed the projectbox yesterday. It is looking good (well good enough) and I was eager to wrap-up the project. Just a few solder joints and it was finished. Before I started soldering, as I final test, I screwed the circuit board in the box and plugged in the power, I opened the magnetic sensor and… nothing happened, at least no audible sound either from the relay or the loudspeaker. I checked the voltage on the noise making part of the circuit, nothing. Then I checked the relay part. I measured voltage but the relay will not energize. Probably something has happened when I screwed the circuit board. Now I’m stuck with a nearly finished projectbox and an apparently broken circuit.

When frustration builds up I have learned to leave a project alone. You might end up throwing the project out of the window. On the up-side this may be a learning opportunity. On page 139 of Make:Electronics is an explanation how to trace faults in a circuit. I had no need for that until now. It is also an opportunity to use the minigrabber (see Figure 3-6 of the book) that I had recently bought.

Inside of the finished project box. On the lid two leds, switch, loudspeaker and banana plugs. On the left side the connector for the power.
Exterior of the finished project box
The minigrabbers. Hopefully they will be helpful to find the fault in the circuit

Building an Intrusion alarm part 3

I solved the problem with the circuit. I simply forgot to place a single wire that powers the coil. After this I was ready to solder the complete circuit on the Adafruit perfboard. I started with the noise making part of the circuit and tested it. Then I continued with the sensor and the relay part. It’s strangely exciting to power the board for the first time and hope it works fine. In my case it did so no frustrating fault tracing although one can learn a lot from this. I’m happy with the result but I now need some components before I’m able to finish experiment 15.  This experiment includes placing the soldered board in a project box and add some user control to the intrusion alarm.

Completed circuit on the perfboard.

Overview of the perfboard, magnetic sensor and loudspeaker.