stumped need help

[lowkey235]

I' been trying to control 12 vdc wiper motors and I keep frying my micro controllers ( lately a bs2 from parallax)
here is the motor control circuit www.me.umn.edu/courses/.../bidirectional/bidirMotor.html
I was trying to trigger with a security light sensor, I am thinking of moving to a prop2 and pir sensor but want to know whats going wrong before i burn up another 100 dollars the tip 120 in the circuit were getting very hot
the motors are to lower props then raise them after a delay

[JonnyMac]

I would suggest using an Parallax HB-25 for the windshield wiper motor; Scary Terry demonstrated this with a Prop-1 and it was very effective.  The HB-25 takes a servo pulse and turns it into the correct PWM/H-Bridge control required for direction and speed control of heavy motors.

[lowkey235]

how many motors will a hb 25 control? I have a little sticker shock about the $50 if tis per motor, also any insight into what could of been the problem that caused the death of my last stamp?

[JonnyMac]

Just one -- and get over the sticker shock; what you want isn't easy to do (and if you built a proper h-bridge the parts and time would be worth way more than $50).   ;D

I don't know how you connected the motor to your now-dead Stamp but you probably didn't protect the Stamp from the horrible inductive kick-back from big motors; the HB-25 takes care of this little annoyance as well.

Now, if you can live with nothing but directional control and give up two outputs per motor you can do it with a relay that is available from All Electronics (one of my favorite places in L.A.):

Here's the relay:
-- http://www.allelectronics.com/make-a-store/item/RLY-525/DUAL-12-VDC-RELAYS-DOOR-LOCK-RELAY-/1.html

[lowkey235]

it was connected like this on a breadboard

will this work if i optoisolate the relay circuit like this?

all I really need is the direction control so I will look into your relays

[lowkey235]

I guess the flyback was killing my stamps, as far as sticker shock you showed me a $2 dollar soultion to the problem will the recomended relay solve the problem of inductive kickback? thanks for the help srry about the first picture it wasnt that big in its properties

[JonnyMac]

The relay above (RLY-525 from A.E.) -- found by all around cool guy, Jeff Davis (www.davisgraveyard.com) -- is really a better solution than your circuit or mine; it does exactly the same thing (direction and on/off control) with two outputs and connects right to the OUTx and GND terminals.  No fuss or muss with any interface circuitry.  You should use a completely separate supply for the motor (which needs a couple amps, I think) and connect to terminals D and C.  Since the motor supply is also powering the relays you'll need to connect the ground side of the motor supply to the GND terminal of the Prop-2.

The relay is configured as an Exclusive-OR circuit so you need only one output on for activity in either direction:

Motor	OUT0	OUT1
Stop	Off	Off
Forward	On	Off
Reverse	Off	On
Stop	On	On

[JonnyMac]

I guess the flyback was killing my stamps, as far as sticker shock you showed me a $2 dollar solution to the problem will the recommended relay solve the problem of inductive kickback? thanks for the help

To be fair, it solves your problem but is not the same thing.  The HB-25 gives you speed control which is needed in many applications -- and I inferred was needed in yours as you mentioned an h-bridge.  I helped a friend here with a flying bat prop that needed very precise speed control over the motor; the HB-25 did the trick.

[lowkey235]

thanks again, If it was up to me I would use the HB-25 however its on the bosses dime and he says keep it cheap, he's not too happy I killed the last stamp...well thats what he gets for getting me in over my head on a deadline lol, will I need to isolate the relay ? will there be inductive kickback on a prop 2 or prop 1?

[JonnyMac]

There shouldn't be a problem because the relays are not connected to the positive side of the Prop-2 power supply (the relays are powered from an external source, same as the motor).  If you want to be extra careful, though, you can connect a 1N4001 diode across each relay coil.

For simplicity you can connect the 1N4001s right to the Prop-2 terminal block.  The anode (+) side of each will connect to the GND terminal, connect one diode's cathode (-, stripe) to OUT0, connect the other to OUT1.  Just to reiterated, for the protection diodes and this circuit the GND terminal will be common to both and will get the anode (+) side of each diode.