Machine Controller Rebuild by a Programmer

[Anxious]

Ok I get all the digital stuff, it's the volts ohms and amps that more or less leaves my head spinning.

My controller on my mid 90's Vytek router died. It faults on the pendent during initial startup home.

New Controller: PC Running Mach 3 or EMC2 -> Cambell Combo BOB -> Gecko G203V - Stepper Motors (PK2913-02AA for X and Y, and PK268-03AA for the Z).

The PS was pushing 91V, so I'm replacing the transformer with a slightly smaller one that should produce a steady 68V and not pulse over the 80v Gecko Limit enough to blow the fuses.

Next is the required Resister to control load... the motor specs for the PK2913-02A indicate 2.8 Phase Amps which falls between 2.5 and 3.0. or 26.1K and 35.25K respectively. The Z uses the PK268-03A at 2.1 Phase Amps. So between 2.0 and 2.5 or 18.8k and 26.1K.

So first am I right to swap the transformer to be more conservative. Clearly 91V is above the 80V G203V limit...

Second, for the current set resister, can I use a couple 33k for the X and Y and a 22K for the Z? I have a resister pack obtained from Radio Shack a number of years ago that includes these resisters. This seems likely to be an analog resister controlling the amps to the motor where the intermediate values are likely very close to the actual calculated need, or do I really need to stick with the half amp intervals shown in the manual?

[CoAMarcus]

You can use a smaller power supply voltage but you do not have to go as low as 68VDC; you can run the G203V right up to 80VDC continuously as it is a soft limit. The actual drop dead voltage of the G203V is around 115VDC so our voltage rating takes ripple and line voltage fluctuations into account.

The current set resistor is not a precision part so you will be fine with those current set resistor ratings. The half amp intervals in the manual are just there for simplicity and you do not have to use those ratings. If you used the formula in the manual to calculate the current set resistor value you would get 31K for the 2.8A motor and 20K for the 2.1A motor. A resistor +/- 10% of this value will work just fine.

It looks like you have a handle on what you need and what you are doing. It is all that digital stuff that makes my head spin... ;-)

Marcus

[Anxious]

Thank you so much, I suppose I could parallel the two transformers yielding slightly under 80v, I didn't see any 20amp ish Toridals that would yield between the 68 and 80 so I just took the biggest under 80 I saw that I could have delivered asap. I'll happily replace it to peak the machine down the road, but I need to get some material cut for a client that has been VERY patient with my rebuild.

So I'll order some extra fuses, see how it goes and adjust as results warrant. Next the digital stuff... Mach 3 or EMC2, but it seems either will do everything the old controller did so it'll likely boil down to how many nice to haves which become minimum requirements for the next machine. For example spindle control, dust collector automation, tool zero function... yes I've thought of a few already, I'll miss the pendent for a short period but looks like either will do that soon too.

Let the fun begin!

Thanks again,
Dave

[andrewilcox]

I dont know what kind of set up you have, but download Oms Law on the internet and that will help you figure it out.

[Anxious]

Andrew you hit a home run with Ohms Law. I hate to admit it, but you are spot on, the beginning is exactly where I am with regard to electricity. I can flip the light on and even replace the bulb, but when it comes to determining when I do and don't need a pull down resister or pull up capacitor... or whichever it is.... I have to dial the phone to get some 411

Thanks