Subject:
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Re: your mail
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Newsgroups:
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lugnet.robotics.handyboard
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Date:
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Thu, 6 Jun 1996 03:19:32 GMT
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Original-From:
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Jeff Keyzer <jkeyzer@calweb.+antispam+com>
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Viewed:
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1852 times
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Yes, the h-bridge circuit is very, very, very confusing. Hmm. Well
it's in my robot right now, so lemme see if I can remember how it works.
Ok, let's see. First, you connect both of the emitters of the PNP power
transistors to +6V or whatever. Then, connect the collector of one PNP to
one side of the motor, and the collector of the other PNP to the other side
of the motor. Then, connect the emitters of the NPN transistors together,
and then to ground. Proceed by connecting the collector of one NPN to one
motor terminal, and the collector of the other to the other motor terminal.
Make sure you remember to connect diodes, reverse biased (so they don't
short circuit across the transistors) across the collector and emitter of
the transistors. (Make sure you look at whether each transistor terminal is
+ or -, and then connect the diode so current WON'T flow.) Alright.
Now, connect the collector of one 2n2907 to Q1, and connect the
emitter through a 180ohm resistor to Q4. Do the same with the other 2n2907,
to Q2 and Q3. (Ok, now the resistor might actually be between the collector
and the transistor, I forget which way I did it. Whichever works, both
might!) Then connect your optoisolators through to the 2n2907s. I
inserted another 1K resistor to the bases of the 2n2907's, to be safe. You
might want to note that the handy board motor connector is different from
that of the miniboard, and the optoisolators have to be connected back to
back, so that one polarity of the motor connector turns one on, and
reversing it turns on the other. (Like a bi-color LED works.)
Well, I hope that covers it. It's been a few weeks since I built
the circuit, but beleive me, it was tricky. If it doesn't work for you,
don't despair, just ask me and I'll try to help you out. Once you DO get it
working, it's a VERY nice circuit, and it's serving me faithfully.
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