[Skiroy]

I just got the go ahead at work to install an alarm system I have been working on. I have to get this right. This is all 24VDC and is being tapped into a currently installed 24VDC 2.5A PSU. Its being used in a loader but I am going to tap into it and it already has a breaker.

So basically a Photosensor will shoot a beam at a moving robot. When the beam is not broken for 30 secs the timer which receives its control voltage from the Photosensor will switch on a light stack. And finally the door saftey switch is going to be wired to interupt the +24VDC to the sensor.

I need to know where in my schematic attached do I need to put a fuse or fuses? The light stack says it needs a fuse of 1A but the current consumption is 90mA and the inrush current is 250mA.

The only other devices Im using that draws any current is the Photsensor which is this sensor that says Max output is 250Ma but I dont know if that is the normal consumption

Allen Bradley (AB) Photoswitch 42GRU-92LO | eBay

And a timer which says the power consumption is 7ma


So my questions are these.

1. Do I need to have a seperate fuse for the light stack and Sensor, and if so where in my schematic does it need to go?

2.Do I have to worry about arcing at the door saftey switch because the Photo Sensor's +24VDC voltage will be running through it?

3. What size fuse or fuses do I need for each?

4. Is my total possable current draw .5 amps?

Please help I have alot of pressure on me.

[underthetire]

Personally, I would fuse it all at 2 amps just to protect the power supply. In my thinking your dealing with such small numbers, nothing really bad can happen.

[Skiroy]

Personally, I would fuse it all at 2 amps just to protect the power supply. In my thinking your dealing with such small numbers, nothing really bad can happen.

Where on my schematic?

[underthetire]

I would put it right on the output+ side of the power supply.

[Skiroy]

I would put it right on the output+ side of the power supply.

Well it has a breaker then goes to a rail of terminal blocks. I guess I would have to figure out how to disconnect some of the terminal blocks to create my own section of terminals to fuse and use for my stuff?"

[Skiroy]

What about the door switch? It will interrupt the +24VDC to the photo sensor many times a day. Is there any issue with arcing or etc.?

[Skiroy]

Anyone?

Also Im looking at these fuse holders. The UL Class J fuse holders.
McMaster-Carr

But what kind of fuse do I need? a fast acting or time delay fuse?
McMaster-Carr

[TarHeelTom]

I'd use a fast acting fuse. You normally use a time delay fuse when you're trying to start a motor, where the starting current is much higher than the running current.

Any fuse holder will do.

Tom

[Skiroy]

Thank you but I still have the question about the Omron door switch. The total possible max current draw would be .5 A. So if the door switch is run in series with the main power supply to this circuit, is there going to be any concerns with this door switch being opened and closed several times a day? Im just thinking about how you can see arcing when you plug and unplug a cord into a wall socket. Essentially this is what will be happening all day long, but it is all 24VDC.

Do I have any room for concern or am I designing this circuit incorrectly by doing this? I could wire it where it is just in line with the photo sensor switch that goes to the timer coil. This way the current draw from the light stack wont be running through the door switch. Any advice?