High Voltage Switching

Larry_in_Freeport

·ct 4, 2004 - I'd like to be able to switch a 125 VDC (or at the very least 50 VDC) voltage using my Stamp2. The·load current would be small, say 50 ma.· Has anyone done this using something like a RadioShack IRF510? Thanks, Larry in Freeport


Post Edited (Larry_in_Freeport) : 10/5/2004 3:38:55 PM GMT

Jonny555

I am unfamiliar with the irf510 but according to the specs, it doesn't seem to be rated for such high voltage. The spec sheet did not even state maximum voltage but graphs showing performance are working with about 10v max. May I suggest a simple transistor controlling a properly rated relay?

Jonny

Tony Ventura

I would recommend a GTO style thyristor for the job. If your unfamiliar with these devices they're basically an SCR which can be gated on or off. A pulse from the Stamp will turn it on, and a second pulse will turn it off. These can be found with rated working voltages of several KV, so finding one rated at about 200V should be no problem.
Another, perhaps simpler approach, would be to use a power Mosfet.· You need only to supply a steady DC·input to turn the device on, and remove the input signal to turn off.· This could also be easily accomplished using an output pin from the stamp.

Tony

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"I love being an educator...its the only profession in which most customers will demand less for their money."

Post Edited (Tony Ventura) : 10/6/2004 2:47:41 PM GMT

SPENCE

Tony,

where can we find basic teory on gto and are there any devices that ar small.
Not the size of a pie pan (6-12" ) diameter.

Spence

El Paisa

·totally disagreed with the use of a GTO for switching high voltage.

GTO is actually is a Gate Turn Off SCR.

You turn them ON by applying a Gate drive but to Turn Off you should apply to the gate a Negative voltage with sufficient energy to sweep the charge stored in the Gate to Cathode junction.

The·switching high voltage load with a Stamp is a simple proposition, a Mosfet with Vds greater than 200 volts, and logic level Vgs.

Tony Ventura

·I respectfully disagree with your disagreement....to an extent.

GTO's are made specifically to switch high voltages with control on a single gate lead.· Of course, some interface circuitry would be required, such as switching transistors between the stamp and the GTO.· Of course its always difficult to guage how much info a person requires to accomplish any task, especially in this environment.·

I do agree however, as I'd previously stated that a·mosfet would be a more elequent solution, requiring only one output from the stamp.· So in mulling this over....forget about the GTO's use the·mosfet instead.· You'll need one thats rated for a Dss that is above your maximum source voltage...150 or 200V should be fine, and also rated for an Id greater than your load current, assuming that your load is going to be in series with the drain.· A quick internet search should lead you to the right device, or perhaps even a trip to the local radio shack.

Tony

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"I love being an educator...its the only profession in which most customers will demand less for their money."

OTC Instructor

If you can get by with 60 volts DC, the easy way is one of these:

http://www.parallax.com/detail.asp?product_id=27321

It's only $18, and you don't even need the interface board to make it work.

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Bruce Clemens, CET Sr.

Instructor, Electronics and Computer Repair Technology
Ozarks Technical Community College
www.otc.edu