Introduction: Adjustable Power Supply Using Cheap EBay Parts
In this guide we are making a cheap adjustable power supply to help us power our arduino projects, the maximum output of the power supply according to the manufacturers of the parts we used should be around 60W.
The price of the project should be around 20 to 30€, I paid 30 just because I got an expensive housing for the project since I am planning to upgrade it at some point.
Please be carefull when working on projects that use high voltage. Make sure all the cables are insulated and grounded when needed.
Step 1: Tools Needed.
- Soldering Iron
- Hot glue gun
- Painters tape
- Dremmel or Power drill
Step 2: Parts Used.
Parts List at the end of the post.
For the project I used a power supply unit from eBay 12v/5A that costed around 6€, a sketchy buck-boost converter 0.8 – 28V 12A 300W (no way) that costed 3,59€(Spoiler alert: The actual range I got was 0.5v to 12.5v), I would suggest using the LTC 3780 and not the one I used (read the tips at the end).
We will also need 2x 10K Potentiometers (with knobs) to replace the ones on the converster in order to place them on the front panel of the power supply, for those I paid 4€ since I bought them localy, make sure to check the value of the potentiometers on your board in case they are not the same. We will also need a Voltage/Current Display, there are several options out there, but I opted for a nice and cheap LED display that set me back 2,45€. I also used a Power connector with fuse and power switch, you could skip that but it is not advised.
Step 3: Connections.
The connections are pretty straight forward,
the display has 5 wires, the yellow one is for the voltage measurement, so it needs to be connected to the buck/boost converter output. The black and red cables need to be connected to the power supply output, it needs ~12v to operate. There is also another set of black and red that are a bit thicker than the other, those need to be connected between the buck/boost converter and the negative output of your finished power supply.
The connections are shown on the image that I made with my superior copy paste photoshop skills..
I Connected everything and made sure that they work properly, after that I removed the 2 potentiometers from the board and connected the new ones, and tested again to make sure that everyhing still works.
Make sure you check the resistance value on the potentiometers that your converter uses and use the same.
Step 4: Assembly 1.
To make the needed holes and cuts on the project box, I covered the front face with painters tape and sketched on it the places that I will have to cut and drill.
Step 5: Assembly 2.
After everything was done, I removed the tape and installed the display, the potentiometers and the connectors.
Step 6: Assembly 3.
And proceeded to hot glue everything on the project box.
Step 7: Get Your Parts.
Step one was to order the parts, I selected the cheapest options from various sources(China, Thailand and some parts from Malaysia) after that, I waited for about 30 days and as soon as I forgot about them, they arrived.
A visual inspection of the parts, I checked if everything looks ok and that there are no obvious issues, once that was done I placed all the parts in my project box to make sure that they fit.
eBay – Around 20€
- 01x 220v to 12v 5A Power Supply – eBay.de / eBay.com / eBay.co.uk
- 01x Buck boost converter 1 – 30v 30A – eBay.de / eBay.com / eBay.co.uk
- 02x 10K Potentiometer – eBay.de / eBay.com / eBay.co.uk
- 01x Voltage/Current Display – eBay.de / eBay.com / eBay.co.uk
- 01x Power connector with fuse and power switch – eBay.de / eBay.com / eBay.co.uk
- 02x banana plugs / binding posts – eBay.de / eBay.com / eBay.co.uk
- 01x Project box
Optional (you probably have some laying around)
- 07x Connectors – eBay.de / eBay.com / eBay.co.uk
- 01x Power Cable – eBay.de / eBay.com / eBay.co.uk
- Several cables.
Amazon - Around 40€
- 01x 220v to 12v 5A Power Supply – Amazon.de / Amazon.com / Amazon.co.uk
- 01x Buck boost converter 1 – 30v 10A – Amazon.de / Amazon.com / Amazon.co.uk
- 02x 10K Potentiometer – Amazon.de / Amazon.com / Amazon.co.uk
- 01x Voltage/Current Display – Amazon.de / Amazon.com / Amazon.co.uk
- 01x Power connector with fuse and power switch – Amazon.de / Amazon.com / Amazon.co.uk
- 02x banana plugs / binding posts – Amazon.de / Amazon.com / Amazon.co.uk
- 01x Project box
Step 8: Tips
Make sure you insulate all your wires, check the reading on the fuse on the power connector and make sure it is not higher than your power supply specs.
If you use a metalic project box make sure you ground it.
I would also suggest using the LTC 3780 buck boost converter since it is more reliable and it is worth the few extra euros in my opinion.
You could also check on youtube, there is a very detailed and professional video from GreatScott! that uses the LTC3780.