switching high volt AC

ktekx

I'm planning on controlling something called "EL wires" which are electroluminescent wires that require high voltage (around 150v-200v), low current at high frequency AC (400hz). My question is how should i switch this? I was thinking possibly two transistors with a common base tied to a Stamp's output pin?

Ryan Clarke

The operating voltage of EL wire is about 50 ~ 130VAC. Brightness increases with frequency. You will need an inverter of some type- these could be powered by something as simple as a 9 or 12v battery. A Stamp could control the base of a transistor to turn on and off a transformer like this...(which I've done)-

Ryan

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Ryan Clarke
Parallax Tech Support

RClarke@Parallax.com

ktekx

I plan on using an inverter to power the EL, I was just asking about how I can switch it on/off using transistors if it were AC voltage (I plan on sharing multiple EL wires on a single power supply and switching them on/off individually.

Hulk

There was a link posted to this site about a year ago on this forum:
http://www.edn.com/archives/1994/072194/graphs/15di3fg1.htm
Hope it helps!

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Basic stamp Newbie

ktekx

Thanks for the replies, guys, but I don't think I fully understand the link you posted, Hulk. When I was asking earlier about "two transistors" to switch AC source, it appears that a triac is what I was thinking of (I didn't even know those things existed). So can I treat a triac simliarly to a transistor? Do I just connect the base pin to the Stamp and let it drive the load to the EL wire? Sounds simplistic, am I totally missing something?


What I'm trying to do is the equivalent of turning on/off an LED with a transistor using DC source...I'm just looking to do the same thing with AC and EL wire.

Hulk

ktekx,
Try this link:
http://forums.parallax.com/forums/pr.aspx?f=21&m=61194
I think it will give you a great start on interfacing the stamp with triacs.

Edit: I have attached images, author unknown, probably the person that posted the above link.· If not, my apologies to the actual author.

Note: the above link deals extensively with dimming AC lighting.· You may be only interested in on/off so your circuit will be greatly simplified.· You can lose all the zero crossing components as well as the program that controls timing relative to zero crossing.· Also note that the circuits shown mention that they are meant to drive maximum 4 amps resistive.· I believe that El Wire is primarily capacitive, but I don't think that will give the triacs any trouble.· If it does influence performance, try adding some parallel resistance to the El Wire.

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Basic stamp Newbie

Post Edited (Hulk) : 5/24/2006 2:17:35 PM GMT

Paul

Google the·specs on a Fairchild MOC3022·chip. I'm not sure how well it handles a capacitive load tho.

IAI-Captain

Hi, Maybe I've got you wrong, but all you want to do is control High Voltage with Low Voltage, right?
If so why don't you consider using SSRs (Solid state Relays).
Parallax sells such a product under Industrial, on the left hand side bar.
http://www.parallax.com/detail.asp?product_id=31204
the product @ the link will allow you to control up to 4 SSRs
I've been working with the SSRs without the Board from parallax, but ordering it is on my list. I purchased·my SSRs directly though Mouser.com
The part that I'm using, (CX24D5R = Crydom SSR specs are: 3-15Vdc Input/ controls up to/ 240Volts AC@ up to 5Amps),·these parts handle DC power·just the same as·AC, and is 100% compatible with the·part, (CX380D5R),·that Parallax sells.
Simple 4 pin hookup.·+&- low power input 3-15Vdc and two pins AC ~ or DC High voltage.
If need be, The switching time, (Duty cycle), can be·fast. I·tested it with the 1LED.spin program running on a Propeller·chip·and I changed the timing from 1/2sec down to approximately ·7.8ms and the SSR·is switching without a problem.
Note:·I am·switching low power·DC in this application about 9V dc, but it could just as well be 90V AC.
I have worked with EL plates and wires before as well a neon signs and Lasers, most use high Voltage with low current so SSRs are a grate fit for the job,·Switching is one aspect and electrical isolation is another consideration. keeping the low voltage safe from the high ac. if SSRs don’t fit the bill try using high voltage and speed Opto Isolators.
don't have any specs but Digikey.com is a good source for such things.
well, I hope that this helps you out.
Bart

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