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Happy Dude
11-09-2006, 01:18 AM
Hello,

I am trying to hookup·6 solenoids (maximum 2 activated at any moment)·to Stamp though MOSFET circuit, I have not worked much with breadboard in the past, can they handle 24 V DC and 6 Amp current ??? I am not sure how I can find current and voltage rating of breadboards ??

Thanks for help.

Happy Dude

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Tommy Bot
11-09-2006, 01:55 AM
I called "Circuit Specialists" because they are the manufacturer of my breadboard. They had no clue. They said that "the guy" who knows that stuff wasn't there today. He said I could find the info on their website. I told him that I looked there first, but it is not listed with the prduct details.

http://www.circuitspecialists.com·(Great boards, questionable service.)

·Sorry, no help.

·Tommy


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Tommy, I know it wasn't designed to·x, but can you make it·do x·anyway?

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metron9
11-09-2006, 03:43 AM
How about test it? I read you have 2 relays at one time at 6 amps so 3 amps per relay. Just plug it in and run 3 amps continuious and take the breadboards temperature during the test. If it melts or gets hot, then no, otherwise yes. Smelling it during the test is another way but you need some background smelling experiance to do it that way.

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Think outside the BOX!

Tommy Bot
11-09-2006, 04:15 AM
That's cool, if you have money to burn. Trial and error (along with necessity) was the mother of invention. While we sometimes have to go with an educated guess and do a little experimentation, it is wise to search for the answer first if it is available. Melting parts and supplies or bench top and room isn't the wisest experimentation.
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Not being rude Metron9, but the "Let's see if it fries" approach is not the best way to offer advice to a new comer seeking advice.
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Look at it this way: What if the rating on the breadboard is 4A. Then a run with 6A happens to hold up to the touch and smell test, in the short term. After multiple iterations of various tests, everything tastes alright. Just when you get confidence that all is ok, you decide to leave your project running for what ever reason while you go into the kitchen and cook dinner, hungry from all that hard scientific type work. After a series of over current experiments, the properties of the metals have changed. (Breakdown sometimes occurs over time, but when its time, you might not be in front of it when it happens). "Thermal runaway" sets in and we can hope that only the bench top and some components get cooked in the process.
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Thermal Runaway: Component starts to heat, causing excessive heat, causing a decrease in resistance, causing an increase in current, causing excessive heat, causing a decrease in resistance, causing an increase in current... you get the picture.
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Someone is bound to have the answer, I'd be patient. "The guy" at Circuit Specialist who knows, should be back to work soon.·He can't be the only one on this planet who knows the electrical characteristics of the ever elusive North American brown spotted breadboard.·

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Tommy, I know it wasn't designed to·x, but can you make it·do x·anyway?



Post Edited (Tommy Bot) : 11/8/2006 8:20:23 PM GMT

metron9
11-09-2006, 04:32 AM
Thermal Runaway: Component starts to heat, causing excessive heat, causing a decrease in resistance, causing an increase in current, causing excessive heat, causing a decrease in resistance, causing an increase in current... you get the picture.

Yes I do, but in this case lowering the resistance will cool the board. If my assumption is correct you are talking about running voltage in a metal strip at one end and out the metal strip at the other end. The metal strip is 1/2 inch long on the typical breadboard as I assume you are not powering the rails with the load. In any case my original post should have said if it gets warm, then NO as well as hot and melt but that's why I said to watch and measure while you do it.

I would go further and say if it stays cool, bring the amps up to 12 amps. If it stays cool then you have a 2 to 1 safety margin.

Yes, I don't recommend melting plastic, the smoke is very toxic from most plastics.

I only thought you were breadboarding it not using it for production or long term use. That kind of current even if the breadboard could take it would be unwise as a loose connection could very well short. A fuse would be highly recommended for long term use as well as breadboarding in case the teapot boils over and you decide to have some toast.

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Think outside the BOX!

Tommy Bot
11-09-2006, 04:48 AM
(Tommy Said, "Thermal runaway, you get the picture...")
matron9 said "Yes I do, but in this case lowering the resistance will cool the board."




What about "this case" will an increase in current cause a cooling effect on the board? The electrons don't generate THAT much air passing by.


Re-read the post(s).
I'll leave the rest of it alone, I know you're only trying to help. Your comment "That kind of current even if the breadboard could take it would be unwise..." shows that you have a partial grasp on where I'm coming from.

Tommy



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(Frequently heard from other's)

Tommy, I know it wasn't designed to·x, but can you make it·do x·anyway?

·

RDL2004
11-09-2006, 05:42 AM
I don't think I'd trust anything over an amp on a typical breadboard. I doubt the limit is in the metal pieces in the board, but in the actual contact area of the connection. You could always make parallel connections for more capacity.

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- Rick

metron9
11-09-2006, 06:06 AM
RDL2004 has got it, I was only looking at the metal piece, of course that could take it but you would need at least 14 gauge copper wire for 3amps and 20 gauge is pushing the limit of the holes in a breadboard. But the contact area is the weak link and sparks could very well fly with loose connections.

Better run your control wires from the breadboard to the relays soldered to a circuit board.

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Think outside the BOX!

Happy Dude
11-09-2006, 01:30 PM
Hey Guys,

Thanks, I think I·will go with PCB solution for large amp circuit, hope I will not fry some thing ...

Loopy Byteloose
11-09-2006, 05:24 PM
If using a breadboard -- think milliamps.
The connections are merely by friction and the conductors are 20 gauge wire or smaller. Therein lie your limits - high resistance connection, small surface contact.

Regarding voltage, it is generally accepted that 48volts and less presents a signicantly smaller fire harzard from sparking and wires overheating. So I would add 100% safety margin and say not more than 24volts for generic breadboards.

Testing comes in two modes -- Destructive and Non-destructive.

Destructive testing implies that one must always provide a safety proceedure with the test.
And even with non-destrcutive testing, safety can be a significant issue as failure may occur anyway.

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