Alt-BEAM Archive
Message #05397
To: beam@sgiblab.sgi.com
From: Sean Rigter rigter@cafe.net
Date: Fri, 23 Jul 1999 21:28:22 -0700
Subject: [alt-beam] Re: h-bridge problems
I think I know what's wrong but just like solving any other problem, try
to break it down in steps. For example,
1. connect the motor to a 4.5V power supply: does it work?
2. connect the h-bridge through a series 100 ohm 1/2W resistor to the
supply: Bridge V+= 4.5V or else bad bridge.
3. connect 2 parallel LEDs cathode to anode across bridge outputs.
Bridge V+= 4.5V or else bad bridge.
4. For h-bridges that use 2N3904 pre-driver transistors by connect one
(and only one) input to +V. LED1 = on
5. For h-bridges that use 2N3904 pre-driver transistors by connect the
other (and only one) input to +V. LED2 = on
6. For h-bridge that use 2N3906 pre-driver transistors follow step 4
and 5 but connect one input to GND instead.
7. Replace LEDs with motor and repeat step 4-6. Motor should turn slowly
forward and reverse.
8. Connect h-bridge inputs to microcore outputs. Motor should turn
slowly forward and reverse
Oops. Asuming that your ucore outputs are active low and that you are
presently connecting these straight to the bridge inputs, then you need
an active low input bridge (2N3906 input transistors) From your
description it appears that you are using the active high input version
(2N3904 input transistors) which must be be driven only from active
high inverted HC240 outputs of your reverser (or from a Bicore) but if
connected straight to the ucore outputs (and without the 47 ohm test
resistor form step 2) can result in smoke.
9. If oops, then first connect reverser to micro core and connect
h-bridge inputs to reverser outputs.Motor should turn slowly.
Consider connecting LEDs to the reverser outputs instead of the ucore
outputs to provide more interesting information.
10. If step 8 or 9 works ok, remove the 47 ohm resistor and connect
direct to the power supply. Motor should turn normally.
Hope this helps
regards
wilf
David Perry wrote:
> hi,just when everything was working something like this comes
> along...okay, my bots ready to go, i've made the h-bridges, and the
> nervous network and reversers which means i can test. But when i
> hooked up one high power (pn2907, 2n3904, pn2222) 6 transistor
> h-bridge, double checked all connections and with one foul sweep,
> connected the power. But the rear motor, the one i hooked a h-bridge
> to didn't move. I think i can here it pulse in the motor. The
> microcore is doing fine, going around and around. But those darn
> motors won't move. The signal voltage is 2.5 volts going to the
> h-bridge but the h-bridge is only outputing 0.5 volts, and only for
> less than a second as the pulse is on. Please help, you wouldn't want
> all the prizes to go to Darrel :-) David Perry
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