[mike10]

i just bought a fet3 driver board 3 axis
i havent got it yet (still in the mail)
i was wondering if i theres plug ins for e-stop and limits switches
spindel on/off
cooland

in planing on buying nema 34 450 oz motors for X and Y axis

can i use a computer power supply to power these motors?

[ger21]

What are the current and voltage ratings for the motors. You can probably use a computer supply, but you won't get much speed from it. You need higher voltages to go faster.

[mike10]

i just bough a 5 volt 15amp (not a switching) power supply will this work?
the motors are 4.2v 4.7 amp

[ger21]

It will spin the motors, but probably not very fast. Try it and see. You'll probably want at least 24V, but that depends on your needs.

[Don C]

actually the fet 3 or 4 is a unipolor drive. I have a fet 4 and it is a great driver. If you use the 5v 15 amp power supply you motors will work fine with out the power resistors. I use cncpro or deskcnc and they both work real well.

[BigDaddyG]

Mike,
I have bought many FET3's and very happy. I use a 48vdc @ 6 amp to turn mid size 34's. I would be very surprised if 5 vdc will produce much more than enought to see it turn. As for the break out boards. There are many on the market. I just found a source for them yesterday and will be ordering on Friday afternoon. cnc4pc.com. They have a 7 port 5vdc w 2 ports at 12vdc for powering the boards etc. Opto Isolators and safety circuit as well. The whole thing about 105.00usd and the other popular one runs about 150, but is in a much smaller foot print (One board vs. three). Well that is my two cents worth, good luck
Glen

[happytriger2000]

Hi everyone,
I was testing my FET-4 with a 2 phase stepper motor of Voltage= 1.5, Amp=3, wired at the X-terminal of the board, Im using a variable power supply for the motors, and my question is: Do I need a resitor for the motor?

csc

[H500]

I not trying to put down anyone who is satisfied with the fet 3, but I don't want beginners to think that this design is in the same league as the "real" drivers. This is a very simple circuit that will not be able to squeeze much performance out of your motors.

You really need at least 24 volts to get an acceptable speed. At that voltage, you will need to use big expensive power resistors to limit the current. Because this waste a most of the power as heat, you will need a much bigger power supply. This will end up costing more than a "real" driver.

Even worst, since it does not have microstepping, you'e likely to suffer from resonance, making your machine useless for doing circular interpolation.

There is really no reason to use this board other than for learning. Despite the apparent low cost, the true system cost is actually much higher than any of the chopper boards.

[CharlieM]

I am a beginner, I was hopeing to use the FET3 instead of a Xylotex to run 267 oz in steppers. did I waste my hundred and some bucks? I have a 24 volt 5 amp switching power supply. Do I need the resistors?

[ger21]

You will need resistors, and that power supply may not supply enough current, if you're using 3 motors. With the FET boards, you need to add up the current rating for each phase of the motors to get the current required.

[CharlieM]

2.8 amps per phase times 2 = 5.6 amps per motor, times 3 = 16.8 amps total! Another popular driver board vender says his 24 volt 4.5 amp power supply will drive these motors just fine?

I can understand why I will need the resistors to run these motors on 24 volts because they only have 1.1 ohme resistance allowing them to draw the intire 5 amps the power supply has, (not good since the motors are only rated 2.8 amps)

I do have (2) identical 24 volt 5 amp switching power supplys, if I really need all those amps talked about in the first paragraph could I parallel the power supplies getting 10 amps?

[ger21]

The Xylotex would only need the 4.5a total. A chopper drive like the Xylotex (and Geckos) only use at most 2/3 of the current of ONE phase of the motor, because the current is rapidly switched on and off and both coils are never on at the same time.

For anyone just starting out, If Geckos are not in your budget, the best drivers for the money are the bipolar Xylotex, or the Unipolar Choppers from either Xylotex or HobbyCNC. Another good option is the bare boards from http://www.embeddedtronics.com, if you know what you're doing. Imo, the FET board above, as well as most of the unipolar boards you see on Ebay, and a few others, just won't give nearly as good performance as the chopper drives I mentioned. I've read an awful lot of posts from people wondering why they can only go 6-10ipm. They all have the same type of unipolar drives.

[DieGuy]

I gotta say that I am impressed with my Xylotex for an inexpensive setup on a taig mill with 270 Oz/in steppers, I have mine set for about 18 ipm rapids but I think it would probably do much more. The torque is quite impressive and the power supply design is simple to figure out. For smaller projects that require less power and voltage than a full blown Gecko setup I would use them again. In fact my next project may be a smaller mdf or aluminum CNC trim router to play with.

[CharlieM]

I did not know what I was getting into when buying the FET3, I will try to return it, if I can't then, I will still go with the other kind of drivers. I think I know why the Xylotex burnt up on me.

[CharlieM]

They re-funded my money, - - Classie Folks.

[DieGuy]

I did not know what I was getting into when buying the FET3, I will try to return it, if I can't then, I will still go with the other kind of drivers. I think I know why the Xylotex burnt up on me.

Gives us a hint so we don't make the same mistakes! Please. :cheers:

[CharlieM]

My mistake was not knowing what I was doing or how to accomplish it. Read the post by "H500".

I believe the FET-3 is a good component, but there are other things that it needs to interface with and if you don't know what you are doing (like me) then the other boards that were recomended is the way to go.

[H500]

The Xylotex, as well as most other bipolar drivers can be killed if you disconnect a motor while the power is applied. You just need to be careful not to do that.