[Biggs427]

I'm converting the logic of my 3 axis CNC from 5v to 24v.

What kind of amperage will be needed by:

- 3x PNP proximity sensors. LJ12A3-4-Z/AY Inductive Proximity Sensor Switch Detector 4mm DC 6-36V PNP NC | eBay used for homing
- 5x Standard switchs: 3 limits, hold and resume buttons.

The 24v to 5v will be done by a 8 bits optoisolator board. 24V To 5V 8-Channel 8bit Photoelectric Isolation Module Level Voltage Converter PNP Output PLC Signal Module - Pin Board - Arduino, Robotics, Raspberry Pi, ESP8266, Learning DIY, Development board ICStation

I may also use a 24v relay.

I have a DR-15-24 24v 0.63A power supply. Will 0.63A be enough?
DR-15-24 Mean Well | Mouser Canada


Thanks

[Biggs427]

Thanks Russ!

http://www.cnczone.com/forums/cnc-wo...ml#post2073936

[Al_The_Man]

I particularly like the 200A requirement for the Prox! More like 20ma.
Al.

[Biggs427]

I missed the current draw in the description.

At 200mA it looks like I'm going to be at the limit of the PS... I was hoping to use the one I already have but l think I'm going to order a new one.

Thanks Al!

[CNCMAN172]

I agree with Al, that is clearly a misprint, proximity sensors are normally 20mA to maybe 100mA. I would test what you have and bet they work just fine.
Russ

[CNCMAN172]

just for grins, I ran down stairs and looked at the box of Balluff proximity sensors I had, and then looked at their specs. My units do pull 200mA, so my guess is that was the spec on the one you have as well. As you suggested your power supply is a little on the small side, and a 2A 24V supply is really cheap on ebay go with a larger supply.

Russ

[Biggs427]

I've searched this morning to try to find some infos and there's some discrepancies in what I find ... to say the least. This happens a lot with Chinese stuff.

For the same part number, some web site state 200mA, others state 300mA output and 20mA of current consumptions...

I will see if I can measure the current drawn by the device with my multimeter tonight.

What percentage of max current should I aim for all the devices connected to the PS?

[CNCMAN172]

Biggs,
Just pick up this 4A supply from ebay for $14, should address all your 24V needs with ease.
Russ


LRS-100-24 Mean Well 1 OUTPUT 100W 24V 4.2A | eBay

[SteveWill]

20,000Hz???? The board Spec. Limit Conversion Frequency:20KHz is that fast enough????

[CNCMAN172]

Steve,
20KHz for what board?

Russ

[Biggs427]

The optocoupler board has indeed a 20KHz conversion rate.

My machine rapids at 12000mm/min or 200mm/sec. At that speed, this delay gives 0.01mm or 0.0004in of travel

When homing this gives 0.0016mm or 0.000065in which should be precise enough to give me the repeatability I need.

[CNCMAN172]

Keep in mind when homing, which is when these are used you are NOT going at 12000mm/min. All machine have reduced homing speeds. Most people jog the machine close to the homing points and then click home all, this way you can do the operation a little faster. Homing needs to be slow to ensure you get a very accurate position, time after time.

Russ

[Biggs427]

You are right Russ. I was giving the example as if I'd home at full speed, what the delay from the optoocupler would be.

The homing on my machine is done in 2 steps.

First the machine search for the switch at 2000mm/min.

When the switch is triggered, it backs off 3mm then do the real homing at 120mm/min.

At 120mm/min the delay from the optocoupler gives even less travel: 0.0001mm or 0.000004in

I've been using this method since day 1 and so far the repeatability has been quite good.

[SteveWill]

I was thinking that the motor signals would go through, I agree for switches they would be fine.