+5 volt source

[MAS]

I built a 3 axis 320 system with an Amtek power supply. This unit puts out 55 volts and about 14 amps current. It also has a separate 5 volt supply. My question: Is it a no no to use this 5 volt tap to power the encoders, breakout board and the 5 volts for step & direction? I’m thinking I should add a wall transformer for powering the breakout board & geckos.

[PoolQ]

I like to keep the "power" or motor side isolated from the computer side. If you have a common ground you kinda bypass the opto isolators. I use a wall wort for my 5 volts.

[NC Cams]

It can be advantageous to keep ALL circuits that see the "same" 5vdc as common to each other as possible.

Of course, it is mandatory to tie all the grounds together on the DC side whether or not you have the AC sides of them coming from a common receptacle - keep in mind that GROUND and COMMON are NOT necessarily the same tie point.

Do NOT plug a wall bug into one circuit and the computer into another circcuit and then NOT tie the GROUNDS together. THis can cause some real bad ground loop problems - if you HAVE to do this, then you'd better do some optoisolating at/on the BOB.

[Al_The_Man]

Originally Posted by MAS It also has a separate 5 volt supply. My question: Is it a no no to use this 5 volt tap to power the encoders, breakout board and the 5 volts for step & direction? .

You did not mention if it was isolated 5v or not, if it is, you have the option of either using isolated techniques or non-isolated ( all commons at ground potential).
There are two schools of thought and practice, I personally subscribe to the common ground method, but it has to be done methodically using a common ground plate, this includes the service earth ground, all shields and power supply commons,.
Also do not tie to any handy ground point, or use the ground plate as a means of picking up a return for a particular circuit, whether low voltage or high voltage.
Al.

[Torchhead]

The Antec is a separate winding and I would hope a separate return on the +5 if it is regulated. The +5 common on a Gecko is referenced to the PC ground. Most good BOB's will have a source of +5 for the Gecko's that is already referenced back to the PC (logic) side. Also keep in mind that is you want to rig up some way to turn AC power off on a fault it will also remove your +5 volts. That may not matter (and could even be a plus) but it makes the motor power become part of the control power. Newer Gecko 203V drives don't use the +5 common anymore.

[Chris64]

Can anyone tell me a good source for getting a 5vdc power supply? I thought I would have one hanging around but no such luck, so then I went to Fry's thinking they must have one and no luck there either. Even the universal AC adapters only allow for 4.5vdc or 6vdc.

[Chris64]

nevermind...found a couple.

Laptop powersupplies at a surplus store is 5.1 (probably OK) and 3 amp.

Also, I had a Ipod charger that was basically just a wall adapter with a USB port. I cut a USB cable and grabbed 5vdc from that too. It's only 1 watt, so I'm guessing that's about 200 ma. A little low I think, but probably OK.