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Switch load


#1

I am looking for a switch like this.

But something with like 38V 4amp rating (At least that is what the stepper driver Vdd upper bound). And has an Eagle file with it. Anything close would be good too. Thanks much.


#2

4A is quite a lot for a switch, i wouldn’t recommend it. I would suggest you either use a FET or relay with a normal switch.

If you really want a switch that handles that amperage, I have a bunch of these at home:
http://search.digikey.com/scripts/DkSearch/dksus.dll?WT.z_header=search_go&lang=en&site=us&keywords=CH760-ND&x=20&y=5
Which look really great (love the on/off silk). They can be used with quickconnect/quickdisconnect blades made by Molex (or clones). I wouldn’t really suggest running 10A through them though, again I use these with a relay in the car, or FET’s in my lab. These wouldn’t work as PCB mount very well… you could just put two wires into your PCB and then mount this on the enclosure though.


#3

Thanks Mark. :slight_smile: It says 10A @ 125VAC. It seems (from others I saw) those numbers dive down under well under 1A for DC voltage. I could not find any DC ratings on that.


#4

Cutting power to a stepper drive by switching the DC input can lead to bad results. Some types of stepper drives will not tolerate this for to long before giving up the ghost. For an AC powered system I typically recommended cutting the AC to the power supply that feeds the stepper drives. If this is a DC powered system then you may need a cap and bleed-off resistor on the drive side so its DC input does not go open circuit suddenly.

[quote]It says 10A @ 125VAC. It seems (from others I saw) those numbers dive down under well under 1A for DC voltage. I could not find any DC ratings on that.
[/quote]

If there is no DC rating on a switch then it is not suitable for use with DC. Finding DC rated switches for higher currents can be tough. The problem is that breaking higher DC currents can weld contacts together, which can lead to dangerous (or at least very exciting :o ) results.


#5

Ok. What if I just “switch” the 5v bus feeding the stepper driver logic. The 24v supply side would still be hot, but shouldn’t that close ~clean when the logic side goes dark or at least not be powering anything? tia


#6

Let’s start with what you are trying to accomplish. Are you just after a way to disable the stepper motor?


#7

You can switch your 5V rail, but make sure that the inputs to your motor drivers are pulled to a known state.

What motor drivers are you using? Can they be disabled? If they can be disabled, then disable them when you turn the 5V rail off.

If there is no current flowing through the 24V rail, then you can switch that with no issues.


#8

Ok. Here is more. 8-30V can go to high rail. That goes to Pololu Stepper(s) regulator side. This side powers the motors. The stepper board also puts out regulated 5V using the source. This 5V sources the 5V rail which powers both the stepper logic side and the PIC chip. If I switch off the 5V rail, the pic and the stepper board would turn off. Not sure what happens on stepper 30V side at that point?

The point is just have an on/off switch where you can walk up and turn the thing off after use. tia