UV LEDs
 

I'm trying to put in some UV LEDs into my tank. The idea is to charge glow-in-the-dark BBs while they sit in the magazine. The problem I'm running into seems to be one of voltage. I have a few 365 nm 5-mm LEDs, but it seems that 3.0 volts just isn't quite enough...seem to need 3.2V. Anyone know of any UV LEDs that work with 3.0V? I believe that is the voltage on the Taigen/HL headlight circuit.

I'm hoping to work with them in the wavelengths of 365-390 nm. From what I've read, anything above 390 nm glows purple. I'd like to avoid having a purple glow coming from my turret. :p

TIA

You can always use a drop down resistor to drop the voltage to the 3.0V you need. You can buy 5V LED's as well.

Give this a look
http://www.rcuniverse.com/forum/rc-t...rsoft-bbs.html

Perry

Perry, thanks for the response and the link. I had forgotten about that thread. Did you use 5V LEDs on your tank? I'm trying to do exactly what you did, but my LEDs don't seem to be working. I figured the problem was that I wasn't providing enough voltage. I thought the headlight circuit was 3.0V. So, when the LED that I soldered into the tank didn't work, I tested the other ones with a couple of AAs. The AAs don't seem to power the other LEDs, either.

Note: I'm testing in a dark room on teeth and $20 bills. No fluorescence. These are LEDs I got: http://www.ebay.com/itm/1-5-10-20-50...:X:RTQ:US:1123

What might I be doing wrong?

Hi Perry


Nice to see you are still dropping by once in awhile. You were responsible for a lot of innovative thinking around here

You won't see the LED's with the naked eye, they are above our visual spectrum.

I use some UV LED's in one of my tanks and can only see it with a camera or phone.

3V should drive the LED's fine, again you will not see any output since we can't see UV in that spectrum.

Hi Dan,
Yep. I am still around from time to time. I guess you never really lose interest. It just wanes at times. I remember many good times in the past on this board. Ruffled some feathers and had mine ruffled but all is good. Glad to see you have stayed active and have moved the electronics effort ahead in such a productive way.

Perry

For UV LEDs my usual advice is to find a 6V LED and run a 5/6V Ubec up to it or run the Ubec and use a 3.3V inline converter. It may cost a few extra bucks more but will run steady and have the whole chamber charged and ready from the time you start your tank or use a RX controlled switch to activate it.
Also, to view an IR LED, an easy way is to use your phone camera. Try to get a half dark area and point the IR LED at the camera and add power, it should glow on your phone screen.

I'll try it again. I'll finish installing it and see if it lights up the BBs. I knew I wouldn't (or shouldn't) be able to the LED's output, but it should cause the security strip on a bill to flouresce...teeth, too, I think. Couldn't get any of that to happen.

I'm interested; but, I'm not sure that I know what you just said. What is a Ubec? Inline converter...is that a resister? Do you have a wiring diagram that would show where to solder these (positive side, negative side, etc)? How would this affect the overall circuit since I'm tying into the headlight circuit?

Some updates:

I've tried a few sets of UV LEDs. Turns out that most of them will barely work at 3V. However, on close inspection I was able to get slight-to-some glow from them using a 3V button cell (2032). But, it seems that most of them want 3.2-3.4V My most recent effort was to step away from the eBay sources and get some LEDs that have better defined specifications. So, I got a couple of LEDs from Mouser. I got the LEDs in these wavelengths: 405 nm (http://www.mouser.com/ProductDetail/...cHs3daTdohk%3d) and 385 nm (http://www.mouser.com/ProductDetail/...vZdh3xyLUCg%3d).

Both of these worked really well with the button cell battery. Both charged the BB fully within 10 seconds (about the cycle time for the HL airsoft gun). The 405 nm LED left a brighter BB. But, I'm not sure if that is a function of the wavelength or the brightness of the bulb. I believe it's probably the brightness of the bulb (200 mcd vs 100 mcd) rather than the wavelength. I doubt these BBs are manufactured with materials that sensitive to differences in wavelength. That said, the 385 nm bulb left far less visible "residue" light than the 405nm bulb.

However, once I put the 405 nm bulb into my PzIII turret, it glowed a lot less than the button cell battery. In fact, it barely charges the BBs, even after letting it sit for several minutes. I don't have a meter or device that lets me check the currents coming from the battery or the Taigen control board. If someone does, do you know the current supplied to the headlight circuit? These seem to be optimized for 20 mA. I think I'm getting less than that.

One other observation of these with the BBs...light intensity appears to be everything when charging the BBs. A dim light will not charge a BB over a longer period of time. Instead, the BBs seem to come to an equilibrium in which they emit as much light as they absorb. The BB doesn't store much energy to emit as light. So, in a dim light, it reaches equilibrium quickly at a low level and stays there. In brighter light, it absorbs more and emits more.

Question for Perry or Shen: can you provide a source to your UV LEDs (ebay seller, online ventor, etc)? I'm thinking I might need something that needs a lower current.

TIA

Look for a low Forward Voltage to light the LED. Some LED's are 1.2V for instance.

Try Digikey.com they have a searchable product selector.

One solution would be to use an adjustable step down voltage regulator with display to fine tune the voltage to the UV led...
I use them to power the heater element of my smoke units....
http://www.ebay.ca/itm/Buck-Step-dow...item2598bc8296

:cool:

PM'd. Sorry I missed your last few questions! Check your inbox, I have a simple and easy way for ya and pretty cheap too.

So share that with the rest of us?

Sure. Ok so as an example....

• First install a BEC in the lower hull. Use a 3.3V in line converter (drops 5V to 3.3V needed for his lights) or get an step down converter (adjustable)
• Next connect the output of the 3.3V to the extra wires on a 360 kit (such as the MG airsoft variant or even getting one of the IR variants with PLENTY of extra wires to work with) so that you do not have to worry about how many lights you wish to use. Using too much current or too many lights can cause a brownout if connected to say something like the headlights. Best to run power all the time and if you do it this way you can run PLENTY of lights and make those BB's glow like radiation :)
• Use the other side of the 360 slip ring for distributing the lights.
• If using an aftermarket radio system use a RX controlled on/off switch. It is very important that you get the circuit completer rather than the RX powered ones. You want this to complete the circuit rather than relying on outputting the RX power which can also cause a brownout though highly doubtful with such weak lights.

Thats about it. Doing this way will allow you to have a UV light on all the time from the instant you turn on the tank. Adding the RX switch is optional, but at least you can do something with all those extra switches we have :) I'm not trying to push the 360 kits too much, I'm just happy we have options to do stuff like this now! Just think you could use 2 wires for positive and negative and 12 for signals if you wanted! Anytime you need data or power up to the turret the slip rings should be the go to. I suggest you all get the IR with MG as you can always expand later in the future if you choose and just shrink wrap it for now as you plan.