Keychain Voltmeter




Whenever we go outside, there may be need of voltmeter. We may not carry the traditional voltmeter every time. Some times we may forget or we cannot carry simply due to its size. So I had a thought to make a tiny voltmeter as a key chain. While going outside we will carry atleast 1 key. It may be either a vehicle's or a house key. That's why I made the voltmeter as a key chain. It can measure from 3v - 30v DC.

Step 1: Parts Needed

  • LED voltmeter
  • Dupont jumper pin and plastic housing
  • Any plastic box
  • single lead wire
  • super glue

I used tv cable coaxial that comes with plastic housing

Step 2: Making the Probes

Crimp the dupont pins, so they are used as probes.

Step 3: Preparing the Box

Cut the plastic so that LED voltmeter is fitted exactly. Cut a plastic sheet so that it is used as cover.

Step 4: Inserting the Voltmeter

Insert the voltmeter and glue it

Step 5: Making and Fitting the Cap

  • Take two plastic tubes so that one can be inserted into another (I used ball point pen and gel pen refill's).
  • Cut a slot and drill as shown in the pictures.
  • Please follow the pictures for fitting the cap.

Step 6: Making the Lock

  • Cut a plastic refill in to the shape as shown in picture (shape of number 1).
  • Glue it to the box.
  • Cut a slot in to the plastic door so that the refill can slide.

Step 7: Making the Key Ring

Take single lead wire and shape as shown in picture and fit the ring following other pictures.

Step 8: Finally

Our keychain voltmeter is ready



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    8 Discussions


    2 years ago

    If I understand properly you use the source to measure as a supply for the voltmeter ? So you can't measure small voltages under 2V and your voltmeter highly interferes with the precison cos you must feed it.

    1 reply

    Reply 2 years ago

    Thanks for watching. I forgot to mention, it can measure from 3v-30v DC


    2 years ago

    Very Cool I have a couple of questions It looks like the probes store inside is this correct? Also is the pcb store bought?

    1 reply

    Reply 2 years ago

    Thank you. There will be no power in the circuit without connection, so we can safely store probes inside. Yes it is store bought.