Restrict DC-DC buck to 5v

Juz89

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Hi, I was looking into the same sort of thing a few months ago but I am by far from being an electronics expert (Just have a love for electronics).After some research online i have found the following crowbar circuit which i added an inline mini ATO fuse to and some screw terminals for ease of use. I was looking into using a SMD poly fuse but thought it maybe easier just using the ATO fuse. I have designed a PCB for this design also but havent gotten around to getting it produced yet and trialled. @AAH or @David_AVD are you guys able to give any input as to if this circuit design will work.
 
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David_AVD

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Yep, that's the common way to do a crowbar. Since you've done up a design, have you worked out a price they can sell for ?

BTW, convention is to have input on the left and output on the right. :)
 

Juz89

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Yep, that's the common way to do a crowbar. Since you've done up a design, have you worked out a price they can sell for ?

BTW, convention is to have input on the left and output on the right. :)
This was one of my first designs i played with so it wasn't drawn the best so i am going to redraw it. I reopened it to take the screen grab and thought that doesn't look right at all. I have not worked out price they can sell for as im not good with that sort of thing (Usually go less then i really should). I know what they would cost me to get made but due to not having a reflow oven (Looking at building an arduino controlled one) not sure how long it would take me to assemble them. I have made them using 1206 Package size resistors and the LM431 is SOT-23 so i think it wouldn't be too hard to do with the hot air gun on my soldering station.
 

David_AVD

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For a small quantity, I'd possibly hand solder them.

For the reflow oven, I use a Kambrook unit with pizza function ($200 unit, not a $50 unit). No need for fancy timing and curves as the heat ramp time is reasonable and we crack open the door once the solder flows and the heat is off.
 

AAH

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For a small quantity, I'd possibly hand solder them.

For the reflow oven, I use a Kambrook unit with pizza function ($200 unit, not a $50 unit). No need for fancy timing and curves as the heat ramp time is reasonable and we crack open the door once the solder flows and the heat is off.
I use the $50 unit I reckon. I do a pre and post heat on the top of the oven and just monitor the boards while they are in there. Once the solder has flowed I swap them out onto the top for a bit of a cool down ramp, swap the next pcb that was pre-heating and then remove the board to a cooling tray.
 

plasmadrive

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I just saw this thread and thought I would jump in..
1st off, I have used over 60 Buck converters in my display and I have only had one failure and it just shut down never over voltage that I am aware of. It took nothing out with it. If you don't cheap out and try to use the $1 version you will most likely have great results.

If you are still sweating the over voltage, you could always get something like a 5 or 10 watt Zenor and put it on the output. The zenor voltage would depend on the protection you want. You could use a 5.6v 2% for example. Personally, I wouldn't sweat it.. I bought all mine from ProDCtoDC and got the potted versions..
 
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Juz89

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For anyone interested i have sent my design off to the board house to get some PCB's manufactured. Once i receive these i will build and test them to make sure they do function as they are supposed to. Once i am happy with the way they are working i will post them up and find out how much interest there is for them.
 

Juz89

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HI,

I have Buck converters which output to 5 volt.
Is their a way I can restrict the out put to 5 volt between the buck and the pixel strip, by way of a fuse or some type of resistor.

I have heard that when or if the buck fails, the voltage increases, resulting to damage to the pixels

Thanks in advance

Deblen
If is interested i have a working board. I used some existing resistors i had here for the first trial circuit. With this trial board once the input voltage reaches 6v it drops the output voltage to 1.2v then after approx 1 second it will blow the inline fuse. This board will handle 5 Amps. Board size is 40x20mm Can be used with Standard,Mini or micro automotive fuses. On the boards to be used within my show i plan to have the maximum input set at 5.3v. If anyone would like these boards i could change the maximum input voltage to anything requested. Cost of the boards would be $10 each + Postage

 
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