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DNA Dan's discussion about secret drive

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DNA Dan:
That is precisely what I had in mind. Thanks for taking the time to schematic it out. I am not foreign to soldering, but certainly the heat sink was something I would not have thought about. Thanks for the tip.

I ordered the motors and such from solarbotics, however they have a $30 USD minimum. So I ended up purchasing the secret motor drive "just in case" I need to do a plan B. You know reading the instructions for that board again they make mention of using the yellow "enable" wire if you're going to use PWM. I was wondering if this could be useful to add the "logic" function down the road to the setup you just laid out. It seems like if you wire the VDC+ from the power supply to the PWM board (and the secret motor drive), then instead of PWM out to the motor, you connected the output to the yellow lead on the secret motor board you could control it through PWM? I don't know how the ground would play into it, perhaps it would go power supply --> sercret motor drive --> PWM board --> motor. I don't know if you would need to ground on the output side of the secret motor board. (Not sure if it matters). But this should allow the PWM motor control, while supplying constant VDC to the secret motor drive, which could then be controlled through a logic interface. Correct? What are you using for your logic interface from the printer port?

Oh and did you see my comment about the switch? I really like those cherry round ones, but they are listed as ON-OFF. Can't that just we wired with the two jumpers like a regular DPDT switch that is labelled as ON-ON. Or for all intensive puposes are they the same thing?

EDIT: I think I answered my own question regarding the switch. With the on-off, you're missing the third leg to attach to. It needs to be an on-on DPDT 2-way switch. (Or 3-way if I want to incorporate the emergency stop.)

DaOld Man:
There is no interface between the printer port and the secret drive. The printer port is the interface between the computer and the secret drive.
The inputs of the secret drive connect directly to the outputs of the printer port.
the limit switches connect between the ground of the printer port and the inputs of the printer port.
The printer port has 8 easy to use outputs (pins 2 thru 9). These outputs either put out +5vdc when high, or ground when low. This is perfect for the secret drive.
Pins 18 thru 25 on the printer port are grounds. Pins 10 11 12 13 and 15 are inputs into the printer port.

About your idea for connecting the PWM drive directly to the secret drive enable input:
This should work, as long as you keep the power supply to the maximum limit on the secret drive.
You may have to put a 1K resistor on the output terminals of the PWM drive.
This will pull the - Out high when the TR1 is turned off.
Connect the - OUT terminal to the secret drive enable input. The speed output when you turn the pot knob may be backwards from what the site says, but who cares?

This may be the way to go. Then you can use the previous circuit with the SPDT switch and just the two limits to control rotation. The PWM drive will control the speed of the motor by pulsing the Secret drive through it's enable terminal. Good idea. How about drawing me a diagram with Paint to show me how you would hook it up.

DNA Dan:
I took your previous circuit diagram and modified it by adding the PWM controller. I thought the yellow wire on the secret drive was a (+) out controlled. Looking back at your comments and the instructions I now see they ground that lead to enable "off". But shouldn't this be (+) from the PWM controller?  I am at a loss for where the (+) out needs to go. Do we even need it to complete the circuit? I guess I don't understand enough about the PWM circuit to place the wire.

DaOld Man:
The 1Kohm resistor will bring the enable input on the drive high when PWM drive is off. It will be low when PWM drive is on.
Should still work, just that your control on the PWM drive may be backward (turn left increases speed, right decreases).

DNA Dan:
Why would the control be backwards?

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