Alt-BEAM Archive
Message #05403
To: beam@sgiblab.sgi.com beam@sgiblab.sgi.com
From: Sean Rigter rigter@cafe.net
Date: Saturday, 24 July 1999 2:27
Subject: 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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