LED Voltage Indicator

[martin manning]

Here's something I've been fooling around with. It has some possibilities, I think... https://youtu.be/2x0Vt8yaYok

[R.G.]

Clever idea.

I put LEDs on the run-down safety resistors of the filter caps on the Workhorse series. Not good for telling you what the voltage is in any gradated way, but you for sure know that if the LED is on, the cap is still storing a healthy amount of juice, and you could pick which decoupling cap was the place that the DC stopped getting to earlier stages at a glance, without a meter.

I couldn't get anyone excited about it. Amp buyers don't seem to care that another few $0.05 parts makes it safer for a tech.

[xtian]

Well, hey! Welcome to YouTube, Martin! Wake up and smell 2018, here it comes.

[martin manning]

My original thought was that a useful bench tool might be constructed out of this, to be used for checking for voltage and draining caps. The fifth LED becomes the lowest voltage indicator when a negative voltage is applied (that could be a different color, or a bicolor LED could replace both), and of course if an AC voltage is encountered both lowest-voltage LED's will light. Another possibility is to put this on an amp with a VVR, to give a visual indication of the B+ voltage level.

[martin manning]

Well, hey! Welcome to YouTube, Martin! Wake up and smell 2018, here it comes.

Well, this kind of thing just demands a video, don't you think?

[shoggoth]

I use a circuit like this:

http://www.pcbheaven.com/userpages/LED_ ... orklog&p=3

I use high voltage parts, and I connect it to a 5v zener diode instead of directly to ground, so it'll turn off when it hits 5v or so (which is low enough for my taste)

Pat

[martin manning]

I picked up an assortment of colored LEDs to play around with in this circuit, and arranged red-red-orange-yellow for positive voltage, and purple (looks like soft blue) replaces yellow for negative voltages. In the photo below 120VAC is applied to turn on both the yellow and the purple LEDs. Toying with the idea of packaging this up as a probe-like tool presented an opportunity to try out KiCad, an open-source PCB layout software. KiCad is unlimited (this board is outside the limitations on other freeware due to its 7.5" length), and it seems very capable and flexible, and it runs on multiple platforms. It will print just the board outline and traces, with small open dots centered in the pads (which is perfect for DIY fab), or standard Gerber files for a commercial PCB manufacturer. What's not to like?