SparkFun Forums

[innoko]

Hi all! This is my first post here and I am quite new to the world of microcontrollers and wiring and coding and what-have-you, so please forgive any ignorance on my part and feel free to talk to me like a 5-year-old, lol. Anyway, I'm using the Arduino Duemilanove and the EL Escudo to try and control four [approximately] 3' strands of EL wire. The inverter from CooLight.com was out of stock when I ordered, so I'm trying to use an inverter that came with the wire I bought: it was a 7.5' segment wired to a 2AA battery pack with an inverter and a 3-cycle switch.

The first time I set it up, I disassembled the battery pack and wired the inverter/switch directly to the Escudo as instructed in the Escudo user guide. It seemed to work fine and ran through the program when powered by USB, but the wires were extremely dim, so I switched to 9V wall power through the Arduino's barrel jack. Bad idea. I know now that this was probably a dumb mistake but, long story short , the Arduino ran through the program a few times with the wires glowing VERY brightly, then the transistor (D1616) on the inverter board burned up. I don't have time (this is for a class project) or cash to replace the transistor or buy a different inverter, BUT I do have another identical inverter/switch to use. Is there any way to step down the power coming from the 9V wall adapter? Or to use the 3V power from the 2AA battery pack? Thanks for any help or advice!

[esklar81]

innoko,

1. In answer to your specific question: Yes, there are ways to limit the voltage getting to your inverter from your 9V power supply. OTOH, it's not clear that it would be easier or cheaper to include a voltage regulator than to repair or replace the inverter.
2. If you are limitted to using a particular inverter, the best I can suggest is that you find out what the maximum power input ratings (voltage and current) are for that inverter. For example, it may be that your inverter will run happily at 6 V, but you toasted it by feeding it 9 V. So, if you have any specifications on the inverter, please post them. If you don't have any specifications in hand, but can identify the manufacturer and model, you may well be able to find information by poking about the web. If you find a datasheet, post a link to it for us.
3. In your initial configuration, were the wires any brighter if you ran only one at a time? If so, your problem may be supply current, not supply voltage. (Although power is the product of current and voltage, they're not readily interchangeable. Most devices behave rather differently at, for example, 3V and 900 mA than they do at 9V and 300 mA, even though the available power is 2.7W in each case.) You could try putting a couple of 2AA battery packs in parallel, so you get the same voltage but have more available current. If nothing else, increasing available current is a much lower risk thing to do than increasing the voltage.
4. If your remaining inverter is rated for 5 V or more, you might try a different external power supply, such as one designed for USB. The planet is crawling with 5V wall warts, including many cell phone chargers.
5. I can't help you with your time budget, but I point out that the transistor appears to be a $0.10 part.
6. Is there any particular reason you need to run the lighting power through the Arduino? In general, I try to keep output power away from my controller board.

Good Luck,
Eric