SmartStep/3 max input voltage?

[milton d]

The manual says 28VAC or 40VDC max but I'm wondering what the weak link is if the voltage input is 10% high. The transformer I bought to power it has 2 taps rated at 24 & 28VAC but actually measures 27.4 and 31.4VAC under load.

I have the system working OK with the 27.4V tap connected but want to get all the power I can safely get out of it. I'm using it on a lathe so only 2 out of the 3 available drivers are being used at this time plus I have a finned heat sink bolted to the rectifier bridge with a 12V muffin fan blowing on the heatsink and the output chips. Everything is staying very cool (80 deg F) after it's been running for long periods so I'd like to switch to the higher input voltage. Oh, the other thing I've noticed is that the stepper motors don't get warm at all after long periods so that makes me think the system isn't close to being overstressed as connected now.

What do ye knowers of electronic smoke & magic think my chances of it dying prematurely are?

Thanks!
Milton

[Denford Admin]

We had issues with the standard setup when run over 28V - the PSU would shut itself down but it seemed more related to the drivers heating up. ie, it would happen more often when it was (very occasionally) warm weather
If you've got some temperature monitoring and better cooling going on then you could give higher voltage a try. Although I'm not sure it would make a great deal of difference to the performance of the machine-are the axes stalling at the moment ? Getting things mechanically sorted and new stepper motors can make more of a difference.

[milton d]

Thanks for the speedy response! So it sounds like it wouldn't burn out instantly if the input voltage was increased. May be worth a 5 minute test just to see how it goes.

It's being used in an ORAC retrofit using Mach3. It was a bare unit with only the lathe mechanicals and a stripped clean lower unit so I've built it up from scratch. I'm on a tight budget and am using what I had on hand.

Obviously, the SmartStep is weak at only 2 amps but is working pretty well, although slow. The mechanicals are all smooth with no binding, I have modern stepper motors and it's not skipping steps at the moment with the speeds I've set it to. I was hoping that upping the input voltage a bit would give me a bit more power & speed but as you say the output power may stay the same no matter what the input voltage is.

Another thought I had was since I'm only using 2 of the 3 outputs, is there any way of connecting 2 of the outputs together to increase the power to the Z-axis? Wacky idea?

[Denford Admin]

I can't see two drives being connected to the same coils liking it very much !
If you want the best from the Z axis, I'd try getting a 5 Amp drive off ebay or similar..
eg this 5.6Amp for £36: http://www.ebay.co.uk/itm/Cnc-Control-M ... 4abb5567cf

Also read up on the stepper motors specs and see whether you should be wiring it in parallel or series (if it's got more than 4 wires that is)
Different wiring gives you different torque/speed graphs

[milton d]

Yeah, I figured it was a wacky idea but with my meager electronics knowledge I figured I'd ask anyway.

My long-term plan is to upgrade to more powerful drivers & motors but for now I'll do the best I can with what I have. Thanks for your help!