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Electronics Forum / Basics / June 2007building an H-bridge
Could four of these TRIACs be used to build an H-bridge? http://www.mouser.com/search/ProductDetail.aspx?R=Z00607MA_1BA2virtualkey5112000 0virtualkey511-Z00607MA I'm only planning on using 100mA max. Thanks, Michael On Jun 26, 6:42?pm, mrdarr...@gmail.com wrote: > Could four of these TRIACs be used to build an H-bridge? ================================== 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. > On Jun 26, 6:42?pm, mrdarr...@gmail.com wrote: >> Could four of these TRIACs be used to build an H-bridge? [quoted text clipped - 4 lines] > Perhaps you have a new idea to combine these two normally entirely > different applications in a unique and unobvious way? Tell us more. 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. > On Jun 26, 6:42?pm, mrdarr...@gmail.com wrote:> Could four of these TRIACs be used to build an H-bridge? > [quoted text clipped - 4 lines] > Perhaps you have a new idea to combine these two normally entirely > different applications in a unique and unobvious way? Tell us more. 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 >> On Jun 26, 6:42?pm, mrdarr...@gmail.com wrote:> Could four of these TRIACs be used to build an H-bridge? >> [quoted text clipped - 7 lines] >Probably not that unique and unobvious... just wondering if 4 >identical triacs can be used instead of 2 npn and 2 pnp transistors. --- 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.  SignatureJF > >> On Jun 26, 6:42?pm, mrdarr...@gmail.com wrote:> Could four of these TRIACs be used to build an H-bridge? > [quoted text clipped - 12 lines] > once they've been triggered ON that's how they want to stay until > the current through them goes close to zero. 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?) http://en.wikipedia.org/wiki/Triac Michael > Could four of these TRIACs be used to build an H-bridge? > [quoted text clipped - 5 lines] > > Michael 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? http://www.st.com/stonline/products/literature/ds/1373/l6201.pdf Signature----------------------------------------------------------------------- To reply to me directly: Replace privacy.net with: totalise DOT co DOT uk and replace me with gareth.harris >>Could four of these TRIACs be used to build an H-bridge? >> [quoted text clipped - 18 lines] > > http://www.st.com/stonline/products/literature/ds/1373/l6201.pdf GTO's ? Signature"I'm never wrong, once i thought i was, but was mistaken" Real Programmers Do things like this. http://webpages.charter.net/jamie_5 |
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