Anyone familiar with the SMD1 Stepper Motor Driver Kit ? I am trying to figure out how to connect external control to the lugs on the switch assembly (DPDT push switches).

The lugs already have the leads soldered so leads for the following

  • run/hold
  • Counter and Clockwise
  • Power

Really new to the electronic stuff though (Two months in). It could be that I am not understanding how to control the leads so that they behave in a similar fashion to the switches. The kit has already been pre-built the only missing piece is the external controls.

Illustration of the SMD1

Interestingly (at least for me... still grasping), a lead is soldered to the right end of Resistor 3. The manual says the only requirement is that the control's state is equal to 5 vdc when energized. So ... in simple (new to electronics) layman terms how does one connect it say to a breadboard with a 5V supply.


  • \$\begingroup\$ What kit? Who built it? Can you tell us what the SMD1 is exactly, aside from a Stepper driver kit someone somewhere made, at some point? \$\endgroup\$ Commented Mar 28, 2011 at 4:26
  • \$\begingroup\$ @Fake SMD1 is just the model no. for it, I guess it stands for Stepper Motor Driver . Anything that I know is in that manual from Ramsey Electronics. When I meant made, I meant someone assembled the driver already (The driver works well with the motor), I just want to add an External Control. \$\endgroup\$
    – phwd
    Commented Mar 28, 2011 at 4:52

1 Answer 1


Looking at th PCB those 2 DPDT switches are being used as SPST ones - one pin (the middle one) is wired to +V, the other is connected to an input on a chip with a pulldown resistor to ground (R6/10).

If the switches are off then the pin furthest from the panel will be pulled down by the resistor to ground - you could then drive it externally (run that pin and ground to the external controller.

Some caveats: if you accidentally turn the switch on bad stuff could happen - best to drive the signal through a small diode for protection - you also need to be careful about voltages - don't drive the circuit from something with a higher voltage than expected (perhaps snarf the power from that other pin assuming it's 5v)

  • \$\begingroup\$ Alright it is becoming a bit clearer what is going on with the switches. I will take a sleep and try it in a few fours. Thanks for the explanation. \$\endgroup\$
    – phwd
    Commented Mar 28, 2011 at 7:30
  • \$\begingroup\$ Yeah this ending up working. I just wasn't putting the ground wire (The lead out of R3) down. \$\endgroup\$
    – phwd
    Commented Mar 28, 2011 at 20:50

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