Concerning the GlideForce MD122012 Linear Actuator without the feedback potentiometer. This will be used to manually raise and lower a cutting tool. The weight of the tool is about 75 lbs so this actuator should handle it no problem. I want to raise and lower it by manually pressing on a two way momentary toggle switch or maybe a joystick type of controller. I need to be able to precisely move it to the correct height to within about 1/32". Well, I might be able to settle for 1/16" but 1/32" would be better. I’m not sure a linear actuator has that good of resolution to even do this. Once I have everything set up and running I can’t have this thing connected to a computer. Pololu sells both the actuator and the controllers so thought I would ask my questions here. If I buy the Simple Motor Controller G2 18v15 will this allow me to quickly move the tool (at a relatively high speed) to the general area where I need it and then slow down the motor to get it to the precise position? I have no idea how these linear actuators work or how the controllers work. After reading the descriptions for the controller I can’t tell if it will do what I want. I’ve been doing a lot of reading without finding the answers so far.
I just realized I can probably use a simple motor speed controller $15 and a DTDP momentary switch to accomplish this. However it would be cool if I could find some type of joystick that would increase the motor speed the further I pushed it on one direction. That way all motor control (direction and speed) could be performed in one motion. Having a separate toggle switch and speed control knob would make it more difficult but it would be cheap. Still looking around on this site for more info.
It looks like the G2 18v15 controller will accept a joystick input so this just might do the trick for me.
You can use a G2 Simple Motor Controller 18v15 to control the speed of the MD122012 actuator using a joystick with an analog voltage feedback. The actuator is driven by a brushed DC motor, so it is continuous and relatively smooth, so it is difficult to say whether or not you will be able to reliably get 1/32" accuracy, since that will generally depend on the user in that kind of setup.
If you really want accuracy at that kind of level, you might consider using the MD122012-P version of that actuator with a feedback potentiometer with a Jrk G2 24v13 motor controller to do closed-loop feedback control. With this kind of setup, instead of manually adjusting the speed of the actuator until it is in the position you want, you can specify the position directly. You can find more information about configuring the Jrk appropriately on the actuator’s product page. We were able to achieve sub-millimeter accuracy using one of our Jrk motor controllers and a Glideforce actuator doing position control like this, but we have not characterized that accuracy or the mechanical backlash in further detail. This kind of setup would probably be more accurate if you specified the target position digitally, such as through USB using Jrk Configuration Utility software or by writing your own program to control it (either via USB or TTL serial/I2C from a separate microcontroller like an Arduino). Otherwise, if you used a joystick to set the target position, there would likely still be some slop from the user.
Thanks for the information. I was pretty sure the 18v15 controller would work but I was also thinking it might be overkill and a more expensive way to do it. I found a circuit plan ( and optional complete kit ) for a bidirectional controller that can control the speed and direction with one potentiometer. When the potentiometer is dialed to the center position the motor is stopped. Turning the pot to the right starts the motor spinning in the forward direction and the more you turn the pot to the right the faster the motor runs. All the way to the right is forward full speed. All the way to the left is reverse full speed. I can build it for about $30 USD. I already have the actuator and I just tested it with a cheap PWM speed controller and verified I can get extremely small “steps” using a momentary switch with the speed set to it’s lowest setting. I’m moving forward with my build. The 18v15 is a cool little controller though. I may find a project for it yet.