12v Drill hacked to powerfeed for Mini Mill

[ZipSnipe]

I'm thinking this is working with coming off the 555 timer and putting a NO momentary between it and the wiper. I tested it a lil more today with different speeds and letting it run a few minutes to see if anything got hot and all was well.

I do thank you Luc for your help, but I am a lil confused by "remove the ground wire from your motor and short your motor to ground
that should do it"
Short my motor to ground? I am trying to picture this and I am getting nothing, sorry my electronics experience is kindergarten.

 

[ZipSnipe]

Well I am finished , she works good. My motor alignment is still off a lil but not enough to hurt anything. Here is a diagram of how I wired mine

 

[rodw]

Awesome! We want pics of the finished item though!

Glad you finally got it sorted out. I am a bit concerned I will have nothing to do once I can stop reading this thread of your trials and tribulations...

 

[ZipSnipe]

Luc that is why I am on these forums, a big thanx for Troyo for starting this thread. Rod here is a pic from earlier, I will post a video once the mill is put back together.

 

[MCRIPPPer]

potentiometers are almost always wired as voltage dividers. this means that the two outer pins are connected to 0v and V+, and the center pin outputs a voltage between 0 and v+ depending on where the knob is turned. so all the controller does is read the voltage fromt he pot and turn it onto a pwm value. if you override the pot and just feed the right voltage into the controller, you can get a 100% speed. you need to find out if full speed is at low, or high input.

 

[John Rudd]

potentiometers are almost always wired as voltage dividers. this means that the two outer pins are connected to 0v and V+, and the center pin outputs a voltage between 0 and v+ depending on where the knob is turned. so all the controller does is read the voltage fromt he pot and turn it onto a pwm value. if you override the pot and just feed the right voltage into the controller, you can get a 100% speed. you need to find out if full speed is at low, or high input.

you are correct, however.....


Like I said in a previous post, there's no need to do that...

Just by pass the controller altogether by grounding the motor's neg terminal....

Horses and water springs to mind.........Ignore my experience and knowledge if you want...

 

[ZipSnipe]

Like this John? Maybe add a diode so it do feedback into the controller?

 

[TroyO]

Each controller will be a little different. Generally, one argument against grounding the negative lead of the motor is that it's usually "better" to use the control side of the device rather than just shunting power... the switch has to be big enough handle the full amperage load of the motor if you do it that way. Not many momentary switches are rated that high.

Zip, the wiring schematic you posted could be a problem, while it would be fine when the motor was in "fwd" mode, I think when you were in reverse mode you would them be shorting the positive side straight to ground. You would have to tap in to the ground wire after the controller but before the Fwd/Rev switch. (That's just with a quick look, I haven't fully figured out the whole circuit or anything.) Assuming whatever controller you are using works by PWM controlling the ground connection that would work if you can find a big enough switch that's suitable.

McRipper, one thing I figured out on my controller was that you couldn't just put power to the wiper because when the wiper was all the way down (electrically close to GND) when you applied the positive voltage you were essentially shorting through the pot. That was why I went with disconnecting the ground... the wiper gets pulled "high" because there's no ground connected to oppose the positive voltage. there's also no risk of shorting the controller out that way.

Keep at it, whatever it is it's not a waste of time. I'm sure if nothing else you are learning tons! Do you have a circuit diagram for the 555 device you are using? I may be able to help more if I knew how the controller was set up.

 

[MCRIPPPer]

Each controller will be a little different. Generally, one argument against grounding the negative lead of the motor is that it's usually "better" to use the control side of the device rather than just shunting power... the switch has to be big enough handle the full amperage load of the motor if you do it that way. Not many momentary switches are rated that high.

Zip, the wiring schematic you posted could be a problem, while it would be fine when the motor was in "fwd" mode, I think when you were in reverse mode you would them be shorting the positive side straight to ground. You would have to tap in to the ground wire after the controller but before the Fwd/Rev switch. (That's just with a quick look, I haven't fully figured out the whole circuit or anything.) Assuming whatever controller you are using works by PWM controlling the ground connection that would work if you can find a big enough switch that's suitable.

McRipper, one thing I figured out on my controller was that you couldn't just put power to the wiper because when the wiper was all the way down (electrically close to GND) when you applied the positive voltage you were essentially shorting through the pot. That was why I went with disconnecting the ground... the wiper gets pulled "high" because there's no ground connected to oppose the positive voltage. there's also no risk of shorting the controller out that way.

Keep at it, whatever it is it's not a waste of time. I'm sure if nothing else you are learning tons! Do you have a circuit diagram for the 555 device you are using? I may be able to help more if I knew how the controller was set up.

very good points. you are right about the potentiometer not getting along with a switch in some circumstances. but you could remove the potentiometer and apply a voltage to what was connected to the wiper, and "ground".

the best thing would be to find a motor driver with an h bridge so it already has the forward reverse control figured out in the microcontroller or whatever it uses to control the FETs.


you could probably buy a brushed dc motor controller from a hobby shop and build a 555 based circuit to synthesize the signal of an rc receiver.

 

[ZipSnipe]

Thanx Troyo, I was simply trying to figure out if that is what John Rudd meant by grounding the motor. The way I currently have it wired up is in my post#102. This works fine but it does not put the motor to full speed but rather just doubles the speed of the potentiometer.