MC-60 PWM DC controller (surplus center one 8 amp)

[luizdiefenbach]

Hi, this thread is for the MC-60 info and mods. the Mc-60 it the 8amp 130v PWM DC controller that surplus center sells:
http://www.surpluscenter.com/item.as...7&item=11-2449

Any other controller please ask on another thread, thanks a lot.

I have colleted some info on the controller and made a pdf, its attached on this post.

Today in the PDF there are:
* Pin and config resistor info
* Surplus data on the MC60
* PWM speed control mod via parallel port (not entirely complete, as the info was for another dc controller), thanks a lot for Jroque for all the info on this mod.


Somethings cool to have in this thread:

* Complete the PWM speed control mod (resistor info, optoisolator used and configuration of the board and the software will be greatly aprecciated)

* Mods need to be done to plug the MC-60 in 220v ac outlet withou frying the board / get excessive dc voltage on output

* Mods to make the current output higher (more than 8amp)

Any more suggestions?


Please help us that have the MC-60 if you have any info or opinion!

thanks in advance!

[skullworks]

I'm wondering if there might be a way to parallel 2 of these units to double the current output (130VDC 16A peak).

I don't think you can mod the board too much - the traces will only support so much power.

[Al_The_Man]

Originally Posted by skullworks I'm wondering if there might be a way to parallel 2 of these units to double the current output (130VDC 16A peak). I don't think you can mod the board too much - the traces will only support so much power.

I have increased the capacity of similar units by removing the switching SCR's and replacing them with off-board high current stud mount type fixed to a heat sink. The power feed can be ran direct to the SCR and just the firing connections made to the board.
Also I think the original author of the Surplus description sheet has his terms mixed up, as I believe this is a SCR phase angle control, NOT PWM.
Al.

[skullworks]

Its also all greek to me. I can follow a schematic well enough to fab and assemble a circuit board, but when it comes to mods I don't even pretend to have a clue. My degree was metalurgy not electronics, although if time and money had been available I would have camped out at college for 12yrs filling my head with the knowledge I lusted for.

But that is not such a bad thing - as the textbooks in use back then still contained alot of tube circuits... Kinda useless today even though the principles still carry over.

I bought this controller for testing. Ideally I need something that allows me to control spindle speed and direction - feedback from an encoder on the spindle (not the spindle motor).

If using this turns into a duct tape, bubble gum and bailing wire rats nest I just forgo its use and switch to Plan B - Use a robust PWM servo amp with its own dedicated 20A powersupply. I'd rather not as it will cost alot in space and monitary considerations.

Another issue I see forming is the total power draw of my little CNC. The Servo Drive for the axis motors will also be drawing a fair load, then we have our current PC's which suck down 1/2 a kW. I may need more than a single residential breaker will support.

I wonder if the CNC router users have this issue with some of those high speed 18A router motors in addition to the CNC load?

[Al_The_Man]

I think you can find a much better alternative than the Surplus treadmill ones, I have picked up 1.5hp KB SCR models with reversing and tach feedback feature on ebay for ~$35.00 , these are often relabeled Baldor etc.
Whatever the control type you use, the type of speed feed back can vary from simple internal current monitoring to ext. tach etc, it should have at least one type for any kind of speed control, this is one of the features that distinguish the level of quality.
BTW a mod does not have to be 'Haywired', the devices to replace are three wire devices so there is very little in the way of external connections.
Commercial routers use a separate power feed to the spindle and Controlling device (CNC).
Al.

[luizdiefenbach]

Well analisyng the board and the info collected I came with some logical thinking (I don't know much electronics, so please correct me):

Its says that resistor marked as RPS2 on the board if clipped lower the current limiting in near 2 amps, so its logical to think that this resistor it the one that control the current limiting on the board. The resistor has 4 band color: blue, red, green and gold so its a 6200K omhs 5% tolerance resistor.
If we lower this value a little I think the board will raise its current limiting level. this is right?

This will bump up the temperature of the components, but the only components that are heatsinked on the board are five T0-220 components:

they are marked:

D1 - 10ETS08FP - Diode
D2 - 10ETS08FP - Diode
D12 - 10ETS08FP - Diode
Q2 - 25TTS08FP - Phase control SCR
Q3 - 25TTS08FP - Phase control SCR

the datasheet of the 10ETS08FP :
http://www.vishay.com/docs/93485/9348510e.pdf

the datashhet of the 25TTS08FP :
http://www.vishay.com/docs/93703/9370325t.pdf

from the datasheet I understood that the max of the diodes is 10A , this is vey little improvement over 8A. Maybe we can change those diodes to 20ETS08FP (20A)

The SCR on other hand the 25TTS08FP datashet says the SCR can that up to 16A!!

So if we change the diodes for more powerfull ones and keep the componets from overheating its possible to bump up the current of this board to 16A (SCR limit)

To cool down the diodes and the SCR I thought that I could unsolder the components of the board and put them all on a CPU heatsink with a fan cooler.

Please let me know what you think, if this is a good or bad ideia

[WilliamD]

I had a general question about this controller. I don't need it for CNC, just to control 130V dc motor and have variable speed capabilities. I'm actually going to use it for a motor to make a power feeder.

Does this controller just vary the voltage, thus the max watts at lower speeds? Or does it deliver up to 8 amps at lower rpms also? Any help on this would be greatly appreciated.

[Al_The_Man]

The unit will probably deliver its rated current depending on load, this is what decides the current draw, voltage will affect the rpm, without feedback the rpm will drop with load and this will also cause the current to increase.
Al.

[WilliamD]

Ah, I see. So for the unit to maintain RPM, it would need some sort of feedback? Do all DC controllers work like this?

So I would basically want to vary the pot on this controller when the motor is under load. I would act as the "feedback" mechanism. Is this assumption correct? If I saw that the motor was bogging down under load, and falling short of the acceptable RPM, I would just increase the rpm from there?

Thanks again!

[Al_The_Man]

Originally Posted by WilliamD Ah, I see. So for the unit to maintain RPM, it would need some sort of feedback? Do all DC controllers work like this?

All servo's do.
Older DC servo's had two feedback loops, one via a DC tach to the drive and the other encoder to controller, if you are using a pot for your 'controller' then you could use the tach principle with a drive that accepts it, this is called velocity feedback mode.
Some of the simple SCR controllers out there , baldor etc, often include the tach option.
Some use simple current-detection feedback, if the current increases the voltage will try and compensate for speed loss.
Al.

[luizdiefenbach]

Originally Posted by Al_The_Man I have increased the capacity of similar units by removing the switching SCR's and replacing them with off-board high current stud mount type fixed to a heat sink. The power feed can be ran direct to the SCR and just the firing connections made to the board. Also I think the original author of the Surplus description sheet has his terms mixed up, as I believe this is a SCR phase angle control, NOT PWM. Al.

1) Witch SCR did you use? thanks a lot


2) Can someone check these two components marked on PCB as C16 and MOV1?

C16 is a capacitor right? witch value and voltage?
MOV1 looks like a capacitor too, but I really don't know for sure.

The stupid person here tried to plug the board on 220v directly without mods to see if would work.

Now i'm rebuilding the board and if possible with components to work on 220vac

attached is some pictures of the board and burnt components

[Al_The_Man]

I happened to have a couple of NTE5545, but I have found since, the ones I converted are fairly flexible.
You should also replace the two diodes that form the rest of the bridge, with some stud mount higher current, again it is fairly flexible as long as the voltage/current rating is observed.
Coincidentally, Today I converted a Bridgeport drive that went belly-up with a Baldor BC140 unit and just used the existing scr's/diodes.
The Mov/capacitor combination is probably sized for 120vac.
You may have to watch how they reduce the 120 for the low level logic, when going with 220.
The Baldor & KB have a jumper for setting the voltage range.
Al.