Series Power Supply Safety Circuit

[KeepItSimpleStupid]

Remember he's selling these things and remember my mode of operation: Put everything on the table first, no matter how stupid or expensive. My bass had always said, "it's better to buy than build". Me: I went by, if I build it, i want it modular and I don;t want to see it again. So, 25 years later a few of the things I built are still around,

Aside:
One was a nice cabinet for a temperature controller and SCR unit. On/off and INT.EXT switches could be wired. A fuse and 30 A disconnect was on the front. It could accommodate a current limit control. The TC could be a jack, plug or wire.

Others, I don't know their fate, but again, they are of a modular construction. Only issue is that the power connector is a twist-on and can be 120 or 240. The locking IEC cords are really cool.

 

[jocanon]

Hey Ron, thank you for the kind offer. I may take you up on that if it seems like the direction I am going to take. I have 200 of these power supplies sitting in my garage right now, so if I use that part, I will need to buy a lot more...that's the main reason I want to keep it cheap is because I have to buy so many.

 

[ronv]

It's not as easy to implement as it sounds. Getting it started is ok, just a switch across the relay. But to just turn it off in normal operation either takes another switch or some logic because the supply is slow to decay.
Here is rev 2. Basically it just remembers you turned it off and waits for the power supply to fall off or for you to turn it on again.
It's starting to look like a candidate for the messiest schematic contest so you would definitely want to build one or 2 before you do a couple hundred.

 

[jocanon]

awesome, thanks Ron.

 

[Misterbenn]

It will take some time for the supplies to come up as well, you might end up needing to hold the on button for a second to get the thing started.

This is a great example of where a relatively simple problem has relatively complicated solutions.

 

[jocanon]

...This is a great example of where a relatively simple problem has relatively complicated solutions.

Not to change the subject...but I am working on a tax problem right now that sounds very familiar to the above statement! I hear that.

 

[4pyros]

What ever happened to just using two relays and be done with it?
Simple cheep and universal!
Did I miss something?

 

[ronv]

Yes, maybe.
This is also his on off switch so he would like to avoid several switches and minimize wires from the output to his little switch box and indicate a fault. Try making the entire schematic and find parts, then the problems show up.

 

[4pyros]

This could all be hard wired.
Fault indication could be as simple as a 110 volt indicator wired parallel with the relay contacts controlling the power supplies input that would light if one of the relays open.
Use a simple SPST on/off switch to turn the systems off and a momentary "Start" push button to bypass the relays at power up.
Simple and as reliable as the relays and thats just how much you want to spend for a good relay.
No electronics needed.
I would draw it up but don't have time right now but I think you guys know what I am getting at.

 

[ronv]

That would almost work if a two switch on/off switch is ok. I suppose you could label one off/ready and the second one start. Not to user friendly, but maybe ok, but I think the fault light would be on when the off/ready switch is in the ready position.

 

[4pyros]

That would almost work if a two switch on/off switch is ok. I suppose you could label one off/ready and the second one start. Not to user friendly, but maybe ok, but I think the fault light would be on when the off/ready switch is in the ready position.

I would keep the toggle switch labeled On/Off and the push button would be "Start".
Yes the fault lights would go on with the On/Off toggle switch before you press the start but thats a valid fault until you start the system.
Its so Simple its Stupid. LOL

 

[ronv]

I suppose with a good set of instructions it might be ok. Let's se what Jocanon thinks.
To me it's not user friendly. I want on to be on and off to be off - 1 switch.
I want fault to be a fault, not just fault if you pushed switch 2.
But having said that I think you could feature it by saying the red light should be on then go off and the green light go on.
And maybe the same with the 2 switches - off , armed (or something like that) and push to start.

 

[jocanon]

I like the idea of user friendly with just one switch, but I guess it depends on how involved it is to do.

 

[KeepItSimpleStupid]

I have a term: "user hostile" as being the opposite of "user friendly".

 

[jocanon]

lol...that's great "Get your user hostile switched power cord while supplies last!"

 

[ronv]

4pyros idea is certainly simpler. Lets think about it a bit.

 

[KeepItSimpleStupid]

I did a few things that didn't look quite right:

a) I took wires and stuffed them in a 120 V electrical outlets in an individually switched power strip while a piece of equipment was under repair for a few hours.

b) Took a 400 A (secondary side) welder (maybe 3' x 2.5' x 4') and wire-nutted it to a 30 A 208 V circuit in the wall for temporary power to weld one small fitting. That didn't look quite right either.

So, they dubbed these things: Kill-me-quicks.

 

[tvtech]

LOL, great post above KISS.

So good to see someone else out there that knows what they are doing....but sometimes make a stuff up cause they are not thinking properly....like something is not quite right here.....take a chance and bang. .

Happened to me too. I frigging hate that. Now you have to start all over and fix stuff that was never blown in the first place

Oh well, at least we are honest about it .

All the best,
tvtech

 

[ronv]

Here is a take off on 4pyros idea. Gets back to one switch.
Couple of things.
1-The red light will be on when it is plugged in. Maybe not such a bad thing.
2- You will have to hold the off switch in the off position until the power supplies drain or it will turn back on. This might be a problem. Might want to check that time with no load again.

 

[jocanon]

Sounds good ron...I'll check when I get home from work tonight (hopefully before 11pm unlike last night!)