Volt-a-drops

itlives · Post by **itlives** » Wed Mar 14, 2007 5:33 am

Changing to 12 volts.
Using a volt-a-drop, I checked the voltage and it's the same coming out as going in.
Do the volts drop when the circiut is turned on?
Just how hot do they get? Mine is too hot to touch.

MNAirHead · Post by **MNAirHead** » Wed Mar 14, 2007 9:31 am

Do you have a "VoltADrop" website?

I'm thinking a drop resistor is what you have..

Wanting to know we're discussing the same things.

Post by **Marc** » Wed Mar 14, 2007 9:31 am

It's just a resistor. With no current flow, the voltage will read the same. These are a really crude way to run 6V accessories on 12V - they lack stability (the resistance changes with temperature) and as you've discovered can get dangerously hot.
You need to know the normal current draw of your 6V device when operated on 6-6.5V. From that you can use Ohm's law to calculate the series resistance that will be needed to cut 12V in half for that device . NEVER attempt to run more than one load off a single resistor - unless they're all always on simultaneously the resistance can never be correct.
Just what is it you're trying to accomplish? There are probably better solutions.

itlives · Post by **itlives** » Thu Mar 15, 2007 5:32 am

I'm wanting to go the easy route with my wipers. I am running my 6v wipers on a 12v system. I figured just put a drop in line and be done with it. I also have this electric fuel guage that was originally used in a 6v system and I didn't want to take a chance of burning it out.

It's a "hard to find" guage.
As for a volt-a-drop website -no I don't have one . My drop(s) are made by EMPI.

MNAirHead · Post by **MNAirHead** » Thu Mar 15, 2007 8:17 am

Wow.. that is a rare guage.. I've seen only seen one over the years in real life.

Timmy

Post by **Marc** » Thu Mar 15, 2007 9:11 am

You'll find that the wipers will run slowly when you first turn them on and then speed up as the resistor heats up. The gauge will need an independent source for 6V, since the current it draws is negligible compared to the wiper motor it will require a much larger resistance. Personally I'd change the armature on the wiper motor, arguably the best inexpensive solution, and buy a real regulator for the gauge.
http://www2.cip1.com/ProductDetails.asp ... -955-811-B
Next-best choice IMO would be to build a current-limiting device as detailed here: http://groups.google.com/group/rec.auto ... 9ca588b3bc
...this too would only work for the wipers, the gauge would still need an independent regulator - but that's not difficult.

Speedy Jim wrote: ...Pick up a LM7805 voltage regulator (chip device)
at Radio Shack or similar joint.

This is a 5V output regulator
Adding 2 resistors can change the output to 6V as shown:

http://www.rason.org/Projects/regulator/regulator.htm

The LM7805 should be bolted to a small heat sink.
Keep in mind that the heat sink needs to be insulated
from ground...