Intro: How to Make an Led Pulse Circuit
For my first Instructable I want to keep things as simple as possible. So I saw a super easy circuit in the Make: Electronics 1ed book by Charles Platt. It is his pulsing led circuit. This is to help people starting out in electronics to get from schematic to a working prototype. Let's get started!
Step 1: Gather Tools and Materials
- 1x 5x7cm proto board
- 1x 100uF electrolytic capacitor
- 1x 220uF electrolytic capacitor
- 1x 33k ohm resistor
- 3x 1k ohm resistor
- 1x 330 ohm resistor
- 1x 5mm led (any color or size)
- thin solder (lead or lead free)
- 1x 2n6027 transistor
- 1x 9v battery
- 1x 9v battery connector
- 1x spdt slide switch
- Flush cutters
- Soldering iron
- Needlenose pliers
- X-acto knife
- Solder sucker or Solder wick
- Safety goggles
- Vise or Helping hands (optional)
For most of the materials I decided to get it from Ebay because I can order it from one place. That's just easier for me. It's also cheaper since you get many parts that can be used for other projects. Which means that you can make more than one if you wanted to. However one downside to this is that the shipping may take 3-4 weeks. These are just recommedations if you don't know where to find the parts. There are many electronic component retailers online if you choose not to use Ebay as well.
I ran out of 5mm leds so I just used a 10mm I had laying around. The spacing will change if you do use the 5mm led but connect it the same way as the led I used and it will work just as fine.
For the soldering iron I linked a cheap one that it can be used for beginners. I have the Hakko fx 888d and it will last a lifetime but it is not necessary for starting out if you're interested in electronics. You can always update later.
Step 2: Assemble the Circuit
So after you have your tools and components together now it's the time to solder the components to the board.
First things first, I have included the circuit from the book which I highly recommend for electronics. next to that is the circuit diagram for those who cannot read schematics. These were very helpful especially when I was beginning. They are not as intimidating now that I have more experience. With the circuit schematic and diagram we can plan out the layout on the board to know what goes where. I placed the components into position close to the edge so it is easier to cut later. This way I can visualize how they connect on the back when I solder them. Then I take a picture for reference later on.
- I started by soldering the switch on the edge remembering to skip a hole for the 9v battery wires. The solder should look like shiny volcanoes. Anything other than that and it is possibly a cold joint, meaning it is not electrically connected. Touch the iron to the lead to heat it up and add the solder.
- Next solder the resistors. place them in then bend the leads outwards to keep it from falling out. Adjust the resistor by heating the solder and pushing the resistor flush to the board. Repeat the process for the remaining of the resistors in this order: 1k, 33k, 1k, 1k, and 330ohm. Don't clip the leads yet. Some will be used for connections.
- After that, place the transistor in the front of the three resistors in the middle. These will be connected later on. Make sure that the flat part is facing the resistor as the orientation is important. solder the ends to get the position then adjust. While I was doing this I made a solder bridge because I used too much solder. I used the solder sucker to remove that. I then proceeded to solder the middle pin. I added the capacitors too. On the left side from this view is the 220uF capacitor, the right is the 100uF capacitor.
- The resistor closest to the switch, the 1k, will be soldered to the 100uF capacitor's positive lead. I did this by bending the resistor lead in the right direction around the side of the capacitor lead. When the joint was made I cut off the excess and put it into a little plastic dish. I usually save these because they come in handy to make connections without wire.
- I bend all the leads out of the way so I can have a clear view of my joints. This is where there will be solder bridges that connect more than one component. The L shaped joint connects the lead of the transistor, closest to the 100uF capacitor, to the resistors 1k and 33k. The next joint is another L shape but backwards the connect the middle lead of the transistor to the 1k resistors in the middle. Since those two connections are done I clipped off the leads for them. The last lead for the transistor goes to the last resistor, 330ohm.
- For the 220uF capacitor the positive side will connect to the transistor. After soldering cut off the lead. I used the negative lead of the 100uF capacitor to connect with the negative lead of the 220uF capacitor. Leave the lead of the 220uF alone. That is all the connections for the top half of the circuit.
- Moving on to the bottom half of the circuit, I used the negative lead of the 220uF capacitor to join the other 1k resistor lead closest to it. Don't cut that off yet.
- I added the led at this moment now that I was completely sure of the solder connections. I connect the 330ohm to the positive end of the led. The negative side was soldered using the remaining 1k resistor lead. That same lead was used to connect to the negative side of the battery leads.
- The last two resistor leads the have yet to be connected is the inner 1k resistor and the 33k resistor. form a solder bridge between them. clip off the 1k resistor lead but use the 33k lead to connect the positive battery terminal. Again cut off all the extra leads. Finally bridge the inner ad outer leads of the switch to the battery wires.
- That's the whole circuit. The only thing that shouldn't be connected is the outer switch lead. This allows for the circuit to be turned off without the need to remove the battery. Before we test is we need to check for any shorts or mistakes in the circuit. This is to make sure the components or the battery don't get damaged when power is applied. After that's done you can finally plug in your battery and give it a test.
Step 3: Final Product
Well now you have your very own functioning led circuit. I have had a ton of fun making it and using it. The fact that I did it with my own hands and that It works is very exciting for me and I hope you have the same feeling. I would have to say that the only problem I had was the thickness of my solder. It caused lots of blobs and some clean up work. If it was thinner the joints would be more precise and cleaner looking. Also I was a little concerned about the battery swelling and overheating but it just disappeared after a while. I looked into it online and found out that it's because the battery hadn't been used in a long time. Finally to make it more compact you can shorten the 9v battery wires and use double sided tape to mount it on the side or the battery.
For my first Instructable, I consider this a success because the photos came out pretty decently since I don't have a tripod. Though my english writing skills may not be great, I enjoyed making it. I have included videos of the circuit in action. Thanks for reading!