Monday, September 03, 2012
Peltor Sound Trap power LED mod
Peltor Sound Traps are great...
...When you don't accidentally leave them on and drain the batteries.
Most models come with this "external audio connector," but that's not a standard plug. It looks like a proprietary fail connector to me.
It doesn't look so bad. It's not like it costs $30 or something stupid.
Oh wait. It does.
Well I don't need audio in one ear that much. But this plug is a good way to get a connection from the inside without disturbing the earmuffs.
Why not solve both problems at once? Lets set these plugs to run LEDs that turn on when the power is on, so we don't accidentally drain the batteries.
This shouldn't be too hard. Lets start with the right side (with the microphones facing forward).
Click images for full size
Lets get our bearings...
After doing some testing with my multimeter, I found the two power leads that had the same voltage with the dial high or low, and no voltage with the dial clicked off.
Notice the empty dial mounts and used dial connectors are mirrored. This is so the circuit board can be used on the left or right earmuff depending on which side the dial is on. Because both sides are connected, we can solder onto these power leads without disturbing the original soldering.
I traced the connections to the left side of the board, desoldered the stupid plug wires, and put some solder on the mirrored connections (they're the two on the bottom).
The normal operation draws 4.72 mA, with the expected 1200 mAh from a AAA jibing pretty well with the advertised battery life of 200 hours.
The LED will need a resistor in series, so we have different options for LED brightness. All will impact battery life in some way, but none will be as bad as forgetting to turn them off when you're done.
Your selection will likely hinge on where you put your Sound Trap away after use. If it's bright where you put them away, you need a bright LED. If you put it in the dark Man Cave, you can get away with a dim one. I'm using cheapo low output LED, so Your Multimeter May Vary.
At 470 ohms we get brightly lit LED drawing a good 2.3 mA at about 1.8v, and will reduce battery life 49%, making runtime about 102 hours. This brightness is suitable for inside a dark closet or cabinet.
At 3.3k ohms we get a semi-lit LED drawing only .37 mA at about 1.9v, which should only reduce battery life 7.8%, making runtime about 185 hours. This brightness is suitable for inside a dark range bag while outside.
At 10k ohms we get a poorly-lit LED drawing a mere .1 mA which should only reduce battery life 2.1%, making runtime about 196 hours. This brightness is suitable for dark closets.
I'll be using a 470 ohm resistor, because I don't have any damn 3.3k resistors at the moment.
The resistor has been wired in series with the stupid plug wires. The resistor can be on either wire, but the pos/neg must be standardized. I'm keeping my negative toward the mic, so we can see the wire coming out of the plug that is closest to the mic is black. So black one goes to the negative lead.
You can do positive toward the mic if it works out better for your soldering, but just remember to do both sides the same otherwise your LEDs will need to be marked for which side they go on.
Since I don't have any rods that fit into the stupid plug and make a good connection, we're just going to test by bending up an LED.
With the LED facing the preferred direction, make sure your LED's negative pole is in the right hole!
Now we can test it out!
I found a 5/64th" allen fit and conducted well into the stupid plug. Maybe a trip to harbor freight is in order.
The permanent plan for the plug is to insert two rods into the stupid plug, solder the LED to the rods, kink or notch the rods so they will attach firmly to the medium, then surround it with putty epoxy or some other non-conducting material.
This would give you two power lights to remind you to turn off the power, that you can easily remove for when you have to go into stealth ninja operator mode when the tangos come. All with no damage or significant modification to the original function. (C'mon, you weren't really going to spend $60 just to get stereo music into your Sound Traps were you?)
I'll update with the plugs when I get the materials together.
For the left ear muff, there is a slight modification. Because the dial is the same right or left, there is some cross on the leads. Below are the correct solder points.
Click images for full size
NOTE: On the left side, the Yellow wire was the closest to the mic, so it is the negative wire.
DISCLAIMER: I'm not a rocket scientist! If you fuck up your Sound Traps don't come crying to me!
ELECTRONICS DISCLAIMER: My understanding of circuits is still pretty limited! If you know more than I, and I've made a significant mistake, let me know!