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I could use some guidance/assistance

ominoreg

New Member
Hello!
I'm new to the forums. I have done repair work on a lot of different electronics in various fields I've worked in, but not board level repairs other than maybe soldering in a fuse or something along those lines. I guess what I'm trying to say is I'm not very knowledgeable when it comes to setting things up in different ways. I have been kicking around an idea but I'm not sure what the best approach would be to make it work. I use low amperage 12v dc powered gear motors (the small 37mm diameter, < 1 amp ones) in a lot of projects that I make. I normally use a small PWM with a small switching power supply/wall wart to drive the motors, adjust the speed and change direction of the shaft rotation. This setup works perfectly fine for my use as far as speed control goes, but it isn't ideal. I have to run wires all over the place to remotely control my speed and direction of rotation because where I'm working on something the motor is turning for me, I may be as far away as 12 feet from the motor. I would really like to figure out some way to wirelessly adjust the pwm via a radio frequency foot pedal. The maximum distance of the signal from the foot pedal to the pwm would be around 20 feet (6 meters). I've looked at motorized potentiometers and wireless boards that interface with an Arduino or similar controller and also servo motors that can adjust a potentiometer but I haven't found anything quite like what I'm looking for or I'm just not understanding how to implement it. The PWM I'm using has a 100k linear pot that has a signal voltage range of 0v-5v that adjusts the duty cycle of the PWM from 1% to 95% (if I remember right) and it also has an off position on the pot that shuts off the PWM. I'm not opposed to using something other than the PWM to control speed and direction, but the little off the shelf PWM I use does work very well for my application and is very affordable (around $5 usually). Ideally, I would like a wireless foot pedal that somehow senses the position of the pedal and transmits that information wirelessly to a controller mounted near the motor that would adjust the speed. I can live without wireless polarity reversing to the motor, although it would be even better if I could have that built into the foot controller as well with a button that could send a signal to something on the receiving end that would be able to act as a DPDT switch on the output side of the PWM. I can fabricate a foot pedal to drive the wireless components from a mechanical standpoint...that is something I'm actually very good at, but the electronics end of things is where I am struggling to find solutions. Ideally, I'd like to be able to do all of that on the electronics side of things at a cost of below $50 (not including the motor). That may not even be possible.
I enjoy learning new things so I'm willing to do the homework but I am trying to figure out what I need to be studying if that makes sense. If some of you were tasked with such a project, how would you go about making it happen? My main goal is to remove the cord trip hazard and be able to wirelessly control the speed of the little 12v gear motor via a foot pedal with downward pressure increasing the speed, upward pressure decreasing the speed. I think it would have to be RF because getting line of sight for IR would be difficult at times because the position of the foot pedal would be different depending on what I'm doing and where I have to move the foot pedal. I hope I provided enough details, but if not please let me know. Thanks in advance to anyone who has some ideas on the subject! Any thoughts would be much appreciated!
 

gophert

Well-Known Member
Most Helpful Member
How often are you updating the speed?

How fast (from button press to PWM change) do you expect (seconds?, 0.25 seconds or "instant" or ...).

How many steps do you want - off to full power? As button presses or as a slider potentiometer?

Is this a one-off personal project or something you want to make many of?
 

ominoreg

New Member
Thank you for taking the time to respond!
The speeds are changed frequently but response time isn't critical. The contraption is used to rotate a long shaft and while working on the shaft, the speed is changed according to what I'm doing (painting, clear coating and other things). It only works for short periods of a time and I like to start it out slowly and increase speed as I work. A delay between pedal movement and speed change is perfectly acceptable, even a full second delay wouldn't have a negative impact for my needs.
The number of steps isn't critical, but I would like off-full speed. With my current PWM, I'm able to get a usable speed range from about 20 rpms up to 200 rpms (full speed of the gear motor I use). Between those points, the speed transition is very smooth using the 270° rotation 100k linear pot. Defined speed steps would work just as well for my needs. 10 steps or more would be perfect. Less would be ok too, but if possible, 10 steps or more would be a little nicer and allow slightly smoother transition as you ramp up the speed I would think.
I would think something with a rotary type of motion would be easier to incorporate into a foot pedal. For example it is pretty easy to make a pulley and string setup to transfer the up and down motion of a foot pedal to a rotary style potentiometer. If a photo resistor could be used as a wireless input somehow that would be easy to incorporate into a foot pedal as well by making a light blocking plate attached to the foot pedal so as you press up and down on the pedal, it covers and uncovers a photo resistor. Button presses would be OK too as long as the signal would be generated repeatedly if a button was held down with something like say a momentary switch. For example, just say the foot pedal has 2 momentary switches on it. One to increase speed and one to decrease speed. If you hold down the switch it could either increase or decrease speed in steps until the switch is released. I hope that makes sense. In my mind, a foot pedal with an up and down motion would be easier to control without looking at the pedal where two switches would be a little tougher to adjust without looking at the switches... although I suppose I could use a seesaw type of foot pedal to actuate a switch. I hadn't actually considered that possibility until just now.
I'm really not sure how many wireless options there are when it comes to wirelessly controlling an analog input like a potentiometer on a PWM.
This would be a one off project for myself. If it works well, I'm sure other people with similar interests may want me to make them some, but it wouldn't need to be a mass produced item by any stretch of the imagination.
Thanks again!
 

gophert

Well-Known Member
Most Helpful Member
Would you expect battery power for the foot switch (transmitter) or is there an outlet near your workstation?
 

ominoreg

New Member
I was thinking that a battery in the foot pedal might be better, although it would be easier to work around a single cord going to the pedal and not to the motor so that is workable as well. Either solution would be fine but I'd prefer a battery powered foot pedal. I guess I should also mention, if transmission is lost for whatever reason (like say a dead battery in the foot pedal) it wouldn't create a major issue. I could just unplug the power on the PWM/motor side of things if it continues to run where it was when connection was lost. It wouldn't be a safety issue or anything like that.
 

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