How To Build a simple 1-25 VDC, SPST NO, 0.05A 1-70 VDC Relay For Under $4

In this Instructable I will show you how to build a 1-70 VDC, SPST NO, 0.05A 1-70 VDC relay for under $4.

Step 1: Gather Materials

Here is a list of things you need for the Instructable.
1-IR led 1.99
1-IR photo transistor 1.59
(they must be IR or the resistance will never stay the same).

Tools
electrical tape

Comments

[.Unknown.]

Say, don't you have to regulate the current to the LED?

[qazwsx755]

Yes you do which i explained in step 3.

[.Unknown.]

Ok then

[osgeld]

its more like a bare bones optoisolator

[qazwsx755]

Yes it is exactly the same as an optoisolator (after figuring out what an optoisolator was).