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Mill Power feed

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John Hill:
Yea, but a pot in series with a resistor is just a pot with less than full travel!  Whenever you use a resistor, pot, or something like a transistor in voltage follower mode you have to dissapate a lot of heat so the components have to be big.

I think the easiest for those who dont want to mess with electronics would be the lamp dimmer, low voltage tranny and the rectification diode.  Providing of course that it works!  I have not tried it! ::)

What is the requirement for a mill feed anyway? A steady slow, controllable, speed?

Darren:
But we don't need the full pot control as we are looking for about a 3-5V variation and the amperage then drop considerably

Duh, sorry John, my mistake, just realised, using a series resistor the voltage will certainly drop but the current won't alter  :bang: :bang:


I do have some CB radio power supplies that use a 2n3055 output. I'm just thinking remove the voltage setting resistor and replace it with a pot.
That might be a very cheap and easy option. These power supplies can be picked up for a fiver or so. A pot is pennies.
This way you even have a tidy case to put it all in.

Darren:
Then use a DPDT switch for forward/reverse, a couple of micro switches to limit bed travel, these could even be adjustable with the mill bed stops.

mickn:
Hi Darren,
You guys certainly know more about electronics than I do.My speed control was via a small dc control unit from Maplins

Panel Mounted Speed Regulator Module


Order Code: RN41U

This I use on the horizontal table feed. Its fed by one  the yellow 12volt supply leads from my old PSU to the windscreenwiper motor. Another 12volt lead supplies the vertical slide. This is purely up and down and saves winding and does not need regulating its on the fast terminals in the other windscreen wiper motor.Sorry I cant be more technical

Mick

Darren:
Thanks Mick, that clarifies things a bit...

The Maplin module can be found here http://www.maplin.co.uk/Module.aspx?ModuleNo=30310&TabID=1&C=SO&U=strat15&doy=search

It's £15.00 + P&P and it's rated at 3amps with a 5A peak. Whilst it would work fine at lower speeds (the current draw drops significantly) it might be on the edge at 12V and deff higher.  Just bear this in mind if you decide to use this and keep those speeds down a touch.

ATX power supplies look good at 30A for a 500W unit, more than enough to power 3 motors at the same time !!! Not that you would want to... :ddb:
With 3, 5 and 12V outputs the choice is mind boggling. I'm assuming you can series connect them?? I'd have to try this to be sure.
But this could give you 3,5,8,12,15,17, 20V speeds on a rotary switch without using a variable power control.
If the unit will let you reverse connect (it might not) there is potential for 2, 3, 5, 7, 8, 9, 12, 15, 17, & 20V Three extra speeds. That would cover all speeds you would ever need. Don't forget the motor also has two speeds as well.
All without any complicated circuitry.

Not sure if I have an ATX power supply unit spare.

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