Stepper Motor Controller / Pulse Generator Modification - Page 1
Forum section: electronics / projects

author: GKHobby
author_rank: Newbie
timestamp: May 16, 2025, 02:02:52 am
content: Hi All,I am adding a stepper motor to a metal lathe to serve as a drive for the leadscrew. I want to use a stepper because in future it will be programmable for other reasons. At any rate, for now I want it to work independently of a computer and got a simple stepper motor driver/pulse generator board. The board came with two dpdt latching switches mounted to the PCB and I want to replace them with toggle switches so I can mount the whole thing in an enclosure. I can't conveniently do that with the switches as they are because they are 90deg to the speed control pot and are shorter than the heatsink for the voltage regulator. The problem with replacing the switches is the pinout on the push button isn’t one I’ve seen before and doesn’t match the dpdt toggles that I have. When the push button is up, the top/middle pins on one side and the middle/bottom on the other are shorted. When the switch is down, the top/bottom pins on both sides are shorted. I don’t see a way to use a regular dpdt to reproduce this pinout. Has anyone come across this before? If so, can you let me know what it’s called so I learn more about it?The first image is the board I am using. The other two are the pinout of the push button that came on the board (excel snippet) and the wiring that I would need to make the dpdt equivalent. The problem is that too many pins would be shorted together regardless of the switch position, so my drawings isn’t actually an equivalent wiring schematic, I just made it to help myself think through the problem. If I can't reproduce the pinout, the next plan is to start probing the states of the pins when its powered to see if they are all necessary. This is a little more than I would like to do, but I'm running low on ideas. I am also open to better versions of the same type of controller, so long as they dont break the bank and arent limited to 24V. This one says its good to 160V or something, so I figure it might be good to about 50, which is enough for me.Please let me know if I need to clarify anything - I've been working on this on and off for a little while so I might be leaving out some detail.

author: ledtester
author_rank: Super Contributor
timestamp: May 16, 2025, 05:05:12 am
content: Does this mapping of pins 1-6 of the PCB switch to a DPDT switch work?In one position of the switch we have 1 and 2 connected and 5 and 6 connected:Code:2 -- o\ /o -- 5\ /1 -- o-+ +-o -- 63 -- o o -- 4In the other position 1 and 3 are connected and 4 and 6 are connected:Code:2 -- o o -- 51 -- o-+ +-o -- 6/ \3 -- o/ \o -- 4

author: shabaz
author_rank: Frequent Contributor
timestamp: May 16, 2025, 08:02:01 am
content: Hi,The two push-buttons controls on your controller board affect the direction and enable/disable connections to the driver most likely. The controller board might be just a 555 chip or a very simple microcontroller, and the large heatsink device might just be part of a voltage regulator circuit..I think you could leave those push-buttons as-is, and just wire your own toggle switches in series with the DIR and ENA connections to your driver module (in other words, wire one connection of a SPST toggle switch to the screw terminal, and wire the other connection of the switch to the wire coming from the driver module, which you unscrewed from that terminal).Then, just set the push-buttons to the position where they supply power on the DIR and ENA pins, and your toggle switches will switch that off since they are in series.

author: GKHobby
author_rank: Newbie
timestamp: May 17, 2025, 01:50:15 am
content: That is a very good idea. I have been so focused on replicating the switch that I stopped thinking about the problem. Thanks for the perspective