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building an H-bridge

Could four of these TRIACs be used to build an H-bridge?

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I'm only planning on using 100mA max.

Thanks,

Michael

Reply to
mrdarrett
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================================== An H-bridge usually is used to get fwd and reverse direction with pwm speed control on a brushed dc motor. A triac is usually used to switch on the AC line to a load like a lamp part way through the half cycle. Perhaps you have a new idea to combine these two normally entirely different applications in a unique and unobvious way? Tell us more.

Reply to
BobG

I can imagine using four SCRs in an H-bridge fed from a full-wave rectifier to drive a permanent-magnet motor in either direction. You could also use two triacs and a center-tapped transformer.

Reply to
Stephen J. Rush

used to build an H-bridge?

Probably not that unique and unobvious... just wondering if 4 identical triacs can be used instead of 2 npn and 2 pnp transistors.

Thanks

Michael

Reply to
mrdarrett

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AC or DC?

Once switched on, triacs stay on until the current falls below the holding current, so in a DC application they would not switch off unless the current is interrupted.

Triacs are normally used in AC applications where the current drops to zero twice in every cycle.

Maybe you could use one of these?

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Reply to
Gareth

used to build an H-bridge?

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With a DC source, it would be difficult to turn the TRIACs off since
once they\'ve been triggered ON that\'s how they want to stay until
the current through them goes close to zero.

With an AC source it would be possible to use the TRIACS to
full-wave rectify the mains and then phase control the input to the
motor, but it wouldn\'t really be PWM since the sine wave "tails"
would persist after the TRIAC was triggered until the mains went
through zero volts.  Then there\'s the snubber which would (more than
likely) have to be used to make sure the current waveform through
the TRIACS would go through zero and allow the TRIAC to turn off.
Reply to
John Fields

be used to build an H-bridge?

Ok, thanks. Guess that's the deal killer right away, then. I wasn't aware of this fundamental feature of triacs.

Just to clarify: when you say "once they've been triggered ON that's how they want to stay until the current through them goes close to zero", you don't mean the current through the gate, do you? (You mean the current through A2 and A1, right?)

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Michael

Reply to
mrdarrett

GTO's ?

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Real Programmers Do things like this.
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Reply to
Jamie

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