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Idiot proof Breadboard Over Voltage protection needed.
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castingflame:
Hey all.

I am in need of a circuit that I can make on vero to use to protect my 3.3v micro-controllers from over-voltage protection on its power lines. 

Scenario: Attaching 12v to the 3v3 supply, breakdown of a 3.3v regulator shorting to 12v, other component failure, human error or plain getting things wrong.

I typically have several voltages on the same breadboard. My power wires are in different colours, I label the breadboard common voltage rails, I label everything. Alas things still go wrong and I am just fed up killing my little BluePills!


I have looked and played with Zeners and tried a few circuits but I am not really happy with any. I need a circuit that goes in between the micro-controller and its power supply so ANYTHING over 3.3v on the 3.3v rail will not get to it.


I know the majority of the time it is my own fault, but it is what it is so I want to try and make a little horizontal circuit on vero that I can just plug into the breadboard between the MCU and its supply.


Thanks for any help.


P.S. Please treat m gently!
ogden:
Fuse + n-MOS + voltage supervisor at around 4v or so, like BD5340. Better pick supervisor with push/pull (CMOS) output like BD5340, not open-drain. Circuit is very simple: N-MOS shorts 3.3V rail to ground blowing fuse when voltage of the supervisor IC is reached. Disconnect is worse than crowbar solution I suggest.
castingflame:
Thanks for your response ogden.

Re: BD5337 - CMOS 3.7v threshold voltage detector

From the data sheet ...'When the voltage applied to the VDD pins reaches the applicable threshold voltage, the VOUT terminal
voltage switches from either “High” to “Low” or from “Low” to “High”. '

I have been trying to wrap my head around what you are saying. I have looked at the BD5340 datasheet and from what I understand it can flip/flip its Vout state when its Vdd pin reaches the 'detection threshold' say 3.7v for the BD5337.

Are you saying that BD53xx Vin =3.3v rail, Vout of the BD53xx is then fed into a MOSFETs Gate. Then the Drain to 3.3v and the Source to the fuse and the other side of the fuse to ground? ... 

This is no doubt wrong and I am unsure where the MCU connects (or is it a global 3.3v rail protection?).

So I can understand that this is a very useful component but my limined knowledge is struggling how to put it all together in a diagram.

Thank you so far.
ogden:

--- Quote from: castingflame on February 14, 2019, 03:15:39 pm ---Thanks for your response ogden.

Re: BD5337 - CMOS 3.7v threshold voltage detector

From the data sheet ...'When the voltage applied to the VDD pins reaches the applicable threshold voltage, the VOUT terminal
voltage switches from either “High” to “Low” or from “Low” to “High”. '

--- End quote ---

They mean that treshold voltage can be reached from below or from above. You are interested "reached from below" which means that output goes from low to high. which is what you need to drive logic level N-MOS (with VGS treshold <=2V).


--- Quote ---Are you saying that BD53xx Vin =3.3v rail, Vout of the BD53xx is then fed into a MOSFETs Gate.

--- End quote ---

Yes.


--- Quote ---Then the Drain to 3.3v and the Source to the fuse and the other side of the fuse to ground? ... 

--- End quote ---

Following circuit is more or less functional equivalent.

https://en.wikipedia.org/wiki/Crowbar_(circuit)


It is easy to "convert" this circuit to one I suggested, just put supervisor in place of LM431 and replace triac with logic level N-MOS (VGS treshold <= 2V) with big enough current capability (10 A or so). Just noticed that supoervisor I suggested, have delay function which is bad for your application. You have to find one w/o delay.
castingflame:
YI had the fuse in completely in the wrong place.

I have some heavy duty logic level MOSFETs in stock.

'Just noticed that supervisor I suggested, have delay function which is bad for your application. You have to find one w/o delay.' Okay, will have a search around.

Thanks again. I'll feed back when I have something.
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