Experiment 18: Reaction timer part 1

With the arrival of the Kingbright numeric LED with the correct width (see my earlier post) I was able to continue experiment 18 of the book Make:Electronics (pg. 170). In this experiment the reader will eventually build a reaction timer using the 555 timer chip and 4026 decade counter. The layout of my numeric LED is a little different than the one from the book so I have to change the connections to the 4026 decade counter later in the experiment accordingly.

In the first part of this experiment you simply test display. This is done by sticking the three numeric LED’s in the breadboard and applying voltage to the succesive pins. Before applying the voltage I connected pin three of every LED to the negative site with a resistor in between. Then I connected positive voltage to all the other pins (see image below).

Next I connected a 4026 chip to one numeric LED. Connecting is easy. The only problem is that I needed a lot of connections already while later in this experiment all three LED will be connected. Pressing the tactile switch sometimes prompted the display to skip a number. This effect is described as switch bounce and described on pg. 174 of the book. Apart from that the whole experiment went pretty smooth (see the video below). To be continued.

Applying positive voltage to a pin of the first numeric LED.

Numeric LED connected to the 4026 decade counter.

DIY cushion for bar stool

This week my wife completed a couple of cushions for our DIY bar stools made of scaffolding wood . At the local market she bought fabric and foam. The fabric is of firm upholstery quality in an apple green color. This matches the color of the wood. The foam was already cut at the right size. To make the cushions the fabric for one cushion was cut into two even halfs.  These halfs were sewed together along three sides creating a sleeve. One side was held open to tuck in the foam. The open side of the fabric was then stiched by hand. Now I can sit on the stool for a prolonged amount of time without blocking the bloodcirculation to my legs.

Bar table and stools with cushion.

Fabric and foam.

Foam tucked in.
Detailed view of the bat stool and the cushion.

Experiment 15: Intrusion Alarm finished!

I wanted to continue with experiment 18 of the book Make:Electronics today but discovered that the Kingbright numeral LED’s that I received were the wrong type after all. The width of the component is to small to fit in the breadboard (it is 2/10 inch instead of 3/10 inch). I ordered the 3/10 numeral LED’s right away and decided to revisit the intrusion alarm. A couple of weeks ago I was unable to finish this project. Back then the circuit board worked fine until I connected all the external components to it (see here). I decided to build the external components on the breadboard and connect this to the circuit board. I discovered that the LED connecting the circuit board to the anode caused the problem, possibly due to the drop in voltage of the whole circuit board. Remember that the system needs 12V. If I supply it with 9V the relay refuses to switch. I decided to leave this LED out, soldered all the external components and fit everything in the project box. This time it works without a problem. To bad about the missing red LED that had to indicate that the alarm was armed. The video of the experiment can be found on YouTube.

Image of the finished Intrusion Alarm.

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