Skip to main content

Hi,

I'm wiring an MTH GP20 dummy for lighting. I'm using LED's for the project.  My headlight is a 3V warm white.  I've wired in a 3V voltage regulator coming off of a full wave rectifier.  That's perfect for the headlights.

I have MTH OEM marker light LED's for the marker lights.  I would like to know the input voltage for these.  I've contacted MTH, but have failed to hear back.

Thanks,

Alan

Original Post

Replies sorted oldest to newest

I appreciate your answer. That surprised me as they're so little I would have expected less than 3v. I'll just use the 3v line I have.
Thanks,
Alan
 
Originally Posted by GGG:

5-6 Volts.  Normally those are in series.  If you had a pair parallel wired, there would be a limiting resistor too.  Probably about 150 ohms.  G 

 

Thanks for the information, Gunrunnerjohn.
Don't ask me why, but I can't get them to light in series anyway.  I reverse polarity from LED to LED.  It baffles me.  So instead of opening a book on electrical engineering I just wire them in parallel.  Would the 3V input be appropriate for that, or would I need a resistor(ohm rating?) to the LED's.
Thanks,
Alan
 
Originally Posted by gunrunnerjohn:

A 100 ohm resistor from the 5V supply will light them fine.  3V will not light the series LED's, those ceramic LED's don't start lighting until they reach close to 2 volts.

 

 

 

You still need a current limiting resistor.  If you put 3V on one of those red LED's with no current limiting, it will be dead in short order.  For series use, you have to connect the negative lead of one LED to the positive lead of the next one.  Then you connect the remaining positive and negative leads that are free to the power source.

 

The stock MTH ones are simply wired in series, I just cut the insulation off a set to make sure.  All of the dual ones that I have start to light around 3.5 volts.  At 3.0 volts, there's nothing.  There is no current limiting, so at 5V you'd need the resistor I mentioned.

 

 

MTH has quite a few different variations on there LEDs.  Early where parallel wired, later versions where series, some had current limiting resistors under the insulation, others did not.  All depends on what application it was originally used for.

 

All MTH CV boards I have come across are 6V output.  Some are more complex than others.  150ohms seems to be the standard resistor MTH used on current limiting.  The MTH LEDs for markers are pretty hardy.  G

Add Reply

Post

OGR Publishing, Inc., 1310 Eastside Centre Ct, Ste 6, Mountain Home, AR 72653
800-980-OGRR (6477)
www.ogaugerr.com

×
×
×
×
Link copied to your clipboard.
×
×