Questions tagged [reverse-polarity]
For questions about the operation and/or protection of polarized electronic components when biased in reverse. Consider also using the "protection" tag and/or tag(s) for the polarized components in question (e.g. "diodes").
375 questions
2
votes
3
answers
168
views
Tips to Identify a burnt resistor on PCB
I believe the PCB board may have taken a reverse polarity power input.
I can see what looks like a burnt out resistor.
Any tips how to identify this component at R20?
This is beside the power input ...
- 31
3
votes
2
answers
126
views
DC Auto Polarity Correction with Minimal Drop
I'm designing a system that involves multiple microcontrollers all operating at 5V DC, that are ultimately supplied power via USB (also 5V DC). However, components can be rearranged by the end user, ...
- 131
1
vote
1
answer
109
views
NPN: reverse voltage between collector and base (very small current)
simulate this circuit – Schematic created using CircuitLab
Short version:
When SW1 is closed, and SW2 is open: will the NPN bipolar transistor Q1 survive?
Is there any thing I have to check in ...
- 9,678
0
votes
1
answer
268
views
Will this power enable circuit work?
I have an application for a module in a vehicle, it will be powered by a permanent live from the battery and enabled by the ignition key. I have designed it this way so that I can have the MCU safely ...
- 851
1
vote
2
answers
120
views
How can I get this optocoupler to work with both the Power Supply and 9V battery?
I'm currently working on a project where I have a circuit that needs to be updated since it needs to have some sort of isolation added to the terminal block inputs to prevent the user from damaging ...
- 547
1
vote
1
answer
103
views
Tp4056 module Li-ion reverse polarity protection
I want to use a tp4056 charging module like this both for charging and powering my low power circuit (300uA avg current).
The module doesn't seem to have reverse battery polarity protection so i have ...
- 41
3
votes
3
answers
256
views
P channel MOSFET for Reverse polarity Protection
I was trying to understand the reverse polarity protection circuit using a P-channel MOSFET.
I understand the purpose of adding a Zener diode: for instance, if our supply voltage is 24V and we are ...
- 355
2
votes
2
answers
143
views
19V Reverse Polarization Protection Circuit Puts Bench Power Supply into OCP
I am trying to implement this circuit using an LM74700. I followed the MOSFET selection tutorial (available on the datasheet) and there were two good options: IRLB4030PBF and CSD18542KCS.
Due to ...
- 41
6
votes
2
answers
239
views
What are the reverse-bias characteristics of a depletion MOSFET with 0 Vgs?
Consider a depletion MOSFET with the gate tied to the source. When forward-biased, it acts roughly as a current limiter.
simulate this circuit – Schematic created using CircuitLab
I can't find ...
- 31.1k
1
vote
1
answer
106
views
Reverse Polarity Protection and Custom Buck Conversion
I have a setup where a GPS tracker is connected with two parallel batteries, one is truck's battery and the other is a 12 V dry battery. Upon disconnecting the truck's battery, I needed to disconnect ...
- 107
5
votes
2
answers
199
views
Reverse Polarity Protection for PC817 using Bat54H not working
I designed a circuit to derive PC817 Optoisolator with reverse polarity protection using a BAT54H Schottky diode.
My Schematic is
Please ignore the TVS40V component; I used it for ESD protection, ...
- 355
0
votes
0
answers
70
views
Reverse Polarity Circuit Protection Between Two Power Sources
I’m working on a circuit that is primarily powered by a vehicle battery. However, it also requires a backup power source, which is a secondary 12V lead-acid battery with a smaller capacity.
Since this ...
- 49
0
votes
0
answers
57
views
reverse feeding step down transformer 12VAC to get 46VAC @ 60mA (approx 4VA)
I have a project where I need to step 12VAC up to 2 X 23V/CT. This will create a regulated bipolar of supply of +- 25V (typical 317/337 regs) to supply 60mA per DC rail. The 12VAC source has 1A ...
1
vote
1
answer
178
views
Circuit design review: reverse polarity and ESD
Please review my protection circuits for ESD and reverse polarity supply.
I have an existing circuit for a RGBW LED driver (grey portion of diagram below) and want to add some input protection to it (...
- 18.6k
8
votes
5
answers
718
views
Does MOSFET-based polarity protection work with single alkaline cells?
There are various ways to protect against reverse polarity when installing batteries. For example, one possibility is a diode. Unfortunately, diodes have a high voltage drop, sometimes even the ...
- 2,168