Need Help!- Hobby CNC build- power supply vs transformer

[Jimdandy]

Hello, I have done a bit of searching on the forum and couldn't dial in exactly what I was needing as far as info on the the topic of using a power supply vs. the transformer setup that is used in the Hobby CNC package. I have the 200 OZ package.

My question to any and all is pretty much.. can I use a DC power supply instead of the transformer-rectifier-cap setup that is spec'd in the original design?

Here is what I have to use and I am curious if it is possible to use it as well as will there be issues if I do? It is rated at 24V 20A.

http://www.meanwelldirect.co.uk/prod...24/default.htm

I have read that some that have used a PS have encountered missed steps during use.. can anyone dis-spell that idea?

Thanks in advance for any input,even a link to a good post regarding this issue is appreciated.
Lane

[Fastest1]

I dont think there is any difference. I have seen a few posts about alternative power supplies over on the Hobby Cnc forum. It wont be responsible for the missed steps either. Are you a member on the Yahoo group?

[Jimdandy]

Thanks for the response. No I am not a member of the Yahoo group. Are you referring to the HobbyCNC yahoo group?

[ger21]

Both are power supplies. Yours is a switching power supply, and the transformer-cap version are called linear power supplies, I think.
Either will work fine.

[Jimdandy]

thanks, if I was to go the PS route... I would still think the cap would be desirable? Any thoughts on this?

Also would I simply hook the terminals directly to the board?

[CarveOne]

Originally Posted by Jimdandy thanks, if I was to go the PS route... I would still think the cap would be desirable? Any thoughts on this? Also would I simply hook the terminals directly to the board?

The capacitor is what filters (smooths out) the output of the rectifier and it is definitely necessary for either type of power supply. Stepping motors don't much care if the output voltage is regulated or not as long as the voltage drop at full load is not excessive. Switching regulated power supplies get very expensive when you need 48vdc or 72vdc at 20 amps due to the electronic components needed to design one. Easily a few thousand dollars US when purchased new.

The power supply output goes directly to the breakout board, and to the step motor driver(s). Don't "daisy chain" the wires. Use individual wires from the power supply to each individual device that it needs to provide power to.

CarveOne

[Al_The_Man]

According to the spec sheet, the Max ripple is 240mVp-p, if this is at maximum current, then you do not have a lot to worry about, the reason for the low ripple with less capacitance is the much higher frequency the switching supply uses (110khz) over 120hz.
Al.

[Jimdandy]

Thank you both very much!

CarveOne, are you saying that I still need to have the cap inline with the board and PS? Or that inherently there is one in the PS as well?

"The capacitor is what filters (smooths out) the output of the rectifier and it is definitely necessary for either type of power supply"

[CarveOne]

Originally Posted by Jimdandy Thank you both very much! CarveOne, are you saying that I still need to have the cap inline with the board and PS? Or that inherently there is one in the PS as well? "The capacitor is what filters (smooths out) the output of the rectifier and it is definitely necessary for either type of power supply"

Purchased power supplies of either type already have them inside. If you are building a linear power supply using a transformer, rectifier(s), and capacitor you will need to provide them. There is no capacitor in series with the dc output to the board. It would need to be from the dc output to the ground reference. I'm assuming that you are talking about the large value capacitor that is part of the dc power supply circuit.

It is also possible that a much smaller value capacitor could be placed at the break out board power input that would act as a higher frequency noise bypass to the ground reference. This capacitor would not be placed in series with the dc power lead because it would not pass the dc to the board. It would act as a dc blocking capacitor.

CarveOne

[Jimdandy]

Very good! Thank you CarveOne.

[CarveOne]

This Keling Inc. 65vdc power supply document shows the circuit diagram. It also has a regulated dc output. The schematic shows the internal capacitor connections and you can see them in the photo. Two are used in this case because it's probably less cost to use two smaller values in parallel than one higher value single capacitor, and the larger value capacitor may physically exceed a height restriction specification.

CarveOne

[Fastest1]

Yes, Dave Rigotti's (Hobbycnc designer) group

Originally Posted by Jimdandy Thanks for the response. No I am not a member of the Yahoo group. Are you referring to the HobbyCNC yahoo group?