pwm motor conrollers and how to build one to suit the motor available

[Eddie6775]

Something Like a current sensor could be as simple as a single resistor, add a comparator chip (very very cheap) and you have an adjustable current limit. So many ways to do it.
Best plan is work out exactly what you want it to do, build a simple version frst, something very basic and take it from there, two years from now you will have a home lab

the replacement cost is near $200. and as for starting simple and going from there? That's probably the approach I'll take. done allot of tinkering with different components as when my Dad passed away I inherited his "lab" and he was a pack rat! I think I gave away more computers power supplies and automotive electronics stuff than most people will ever buy in there lifetime...lol. I did keep his junk box and parts rack though, so I bet I have what I need rite out in the garage, but I digress. K.I.S.S. works for me. I'm familiar with how comparators work and I can sort of see your avenue of approach there and now that I think about it, I do have some big transistors out there too but I never tried to use them because I couldn't find any specs on them. That; I imagine would be the expensive part. but even spending some money on parts I'm pretty sure I'll come out ahead.

I appreciate everyone's help so far, and once you guys stoke my brains enough I'll even get brave and post a schematic for the group to critique . I love a challenge.

 

[Eddie6775]

I believe your concern about reversing the motor is unfounded, the incident mentioned earlier was probably on a motor that had very worn brushes and hadn't been looked at for ever. Looking at the brushes in you photo, I don't think you'll have a problem.
If you're interested in my design, over current could be done with a single hall effect device, take a toroid core and Dremel a slot in it and glue a $3.20 Honeywell SS490 Series Standard Miniature Ratiometric Linear Hall-Effect Sensor into the slot and run one of your feed wires through it and then compare the output to a set voltage and you have your current limit. You can have your controller for 1 quad opamp and 1 quad comparator IC, under $6.00 for 2 PFETs & 2NFETS and a handful of lesser parts.
Kinarfi

That picture was actually of a new part from the internet, but my brushes didn't look to bad. I keep a set in my machinist chest anyway along with a couple of gears that have a tendency to blow apart while fly cutting if I make a mistake.. I'm still wanting to try the reverse, but I'll add that feature as a second. I got to thinking last night and I have done a reverse before. I picked up an old Hardinge hand screw machine and it couldn't reverse so I set up a simple three way switch; that on the far left was reverse, positive lug on top middle no contact and rite was forward positive on bottom. That's probably what I'll do with the mill too. Now correct me if I'm wrong please but until it was pointed out to me otherwise I thought that was considered an H bridge. Which brings another question. Is an H bridge done strictly electronically? I built one with relays for an electric winch one time, but the hand throw switch....Hmm... I was probably mistaken in calling that an H bridge.

This would be a very simple mod that would save a ton of time and effort though..

 

[kinarfi]

Eddie, read this,https://www.electro-tech-online.com/articles/forward-reverse-variable-speed-motor-controller.650/ it's how my design works, but instead of a Hall device, for your application the first section could be dropped and a pot or rheostat put in it's place.
I suppose that any 2PDT toggle switch or relay could be considered an H Bridge

 

[kinarfi]

**broken link removed**
simple easy way to go, just swap out the 100v fet for a 150 volt fet

 

[kinarfi]

https://www.kitsrus.com/pdf/k166.pdf

 

[Eddie6775]

It looks like you've put some serious thought and allot of nice features into your design. I'm still a little intimidated, so I'll take the following two schematics to the bread board and tinker. I'll have to look close at that first one though...There seems to e allot more going on!

Off to the shop......

 

[kinarfi]

Here's an old design I saved a few years back, for 120 volts, cut the wire between R4 and D3 replace the fet with something that can handle the higher voltage