Alt-BEAM Archive
Message #09523
To: "'beam@sgiblab.sgi.com'" beam@sgiblab.sgi.com
From: Wilf Rigter Wilf.Rigter@powertech.bc.ca
Date: Mon, 24 Jan 2000 21:16:02 -0800
Subject: [alt-beam] BEAM FLIP/FLOP
In response to a question from aggz_666 on the YAHOO BEAMROBOTICS club, I
dragged out an old circuit which I find very BEAMish. I call it the BEAM
flip/flop. A very useful circuit! In this case the momentary closing of the
micro switch causes the motor to reverse.
aggz_666 wrote on 1/23/00 12:27 am Could someone tell me how to make a
circuit where: Press a micro switch, motor reverses. press it again, motor
goes forwards, etc. Ok aggz_666 your wish is my command. You need the
following: Two 74HC14 or 74HC240 inverters are connected in series (1st
inverter output to 2nd inverter input) and a 10K resistor is connected from
the 2nd inverter output to the 1st inverter input. A 1M resistor connected
between the 1st inverter output and one side of a 0.1 uf cap. The other side
of the 0.1 uf cap connected to ground. Then the microswitch is connected
from the 100K resistor/0.1uf cap junction to the 1st inverter input. That's
all it takes to make a BEAM flipflop (FF)! Press the microswitch and the FF
outputs flip, press it again and they flop back again. Can you see how this
works? To control a motor with this circuit you need some motor drivers or
an h-bridge. Connect one motor driver input (can be a spare inverter for a
small motor) to the 1st FF inverter output and a 2nd motor driver input to
2nd FF inverter output. Now connect the motor across the motor driver
outputs and the motor will turn and reverse every time the microswitch is
pressed. If you use the inverters as motor drivers consider using two or
more in parallel to boost the available output current.
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Attachment: BEAMFF.gif
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