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Questions tagged [reverse-polarity]

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2
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1answer
39 views

Circuit protection component arrangement

I was reading this thread and decided that in general it's better to place the reverse polarity protection diode D2 after the TVS rather than before it, and to instead use a bidirectional TVS for D1 (...
0
votes
1answer
101 views

How does this BJT affect the circuit? If it does, how should I simulate on Circuitlab to see the effect?

I am trying to understand how NPN Q23 in the picture below affects the operation of the left circuit. If it doesn't then what we get is the circuit on the right with the only transistor now being Q30....
0
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2answers
83 views

How to tell if a capacitor is still good?

I was replacing a 400v 120uf capacitor in a power supply (ac 120v-19v DC 4.62 amps) well I was a dumb ass and stuck in backwards somehow. I tested the dc out end while it was still plugged in and ...
0
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0answers
43 views

Reverse voltage on MIC5225 in particular and other LDO in general

This question has been asked many times before, for example about LD1117, MCP1703, LM78M05CT, MIC2920A, ADP7142 etc. Why am I asking it again? a) From reading all those topics it seems that the ...
0
votes
1answer
56 views

Can a reverse battery be considered a resistance?

In a simple circuit with 2 batteries and a simple load, one of them supplies 10V and the other 3V. The 3V one is reverse, in a way that the total output of batteries is 7V. Can this 3V battery be ...
0
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1answer
105 views

Reverse voltage protection circuit explanation

Considering this circuit : (The complete schematic can be found following this link - page 23) It is connected on the return path of an IC to provide reverse-voltage protection. I understand that ...
1
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3answers
150 views

A question about reverse polarity protection diode

Is the function of 1N4001 before the 5V regulator reverse polarity protection? Is this a fine method? And I sometimes see 1N4148. Can any diode(besides zener) be used for such function?
1
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3answers
110 views

Reversing P-channel mosfet for polarity protection component selection

Situation: I'm trying to implement a reverse polarity circuit using a p-channel mosfet and a voltage divider using a resistor + schottsky diode. More information here if you need a refresher. The key ...
0
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1answer
54 views

What will happen if P-channel Enhancement type MOSFET gate kept open while connected as diode in real case

[ I am using MOSFET as diode for polarity protection of system. Vehicle supply of 12V is applied to drain & system is connected to source. Gate kept open purpose. I have simulated attached ...
4
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2answers
203 views

High-side vs low-side reverse polarity protection

I need to make a reverse polarity and over-voltage protection for a fairly powerful device (45W @ 12V input) and after some research I noticed a weird peculiarity. A typical reverse polarity ...
1
vote
1answer
43 views

Reverse polarity protection for symmetrical input

I have a symmetrical voltage input I need to protect agains reverse polarity, and over-voltage. Here is the reverse polarity protection I designed. Is it correct ? I can't find much information about ...
0
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1answer
61 views

LED behavior during 24 VAC negative half cycle

I don't understand why the green portion of LED3 is able to conduct. Since the path marked in green represents the negative half-cycle of the 24VAC isn't the green LED reverse biased therefore no ...
0
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1answer
90 views

Reverse Polarity and TVS Diodes Not Working?

This is a follow up to this issue: Damaged TPL7407LA Transistor Array (*Updated With Scope Testing Images*) We are experiencing both reverse polarity and transient voltage spikes in our automotive ...
5
votes
1answer
498 views

Replacing two LEDs with a 2-pin, bicolor LED, using a circuit that reverses polarity based on two inputs

I'm working with a commercially available circuit that can optionally be configured to disable its internal LEDs and use two external LEDs. This post discusses the use of external LEDs. One LED or the ...
0
votes
1answer
160 views

Have I fried the transistor in this circuit?

It was a germanium PNP transistor. I might've pressed the button too. I saw transistors used as capacitors that were connected like this, but they weren't germaniums. What current (if any) has flown ...
1
vote
2answers
139 views

Protecting a power supply from inductive load

I recently got a PeakTech 6225A power supply for my hobby of making/"tinkering"/messing around. I get many parts that I want power separately to diagnose them. I also get a lot of electromotors and ...
0
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0answers
31 views

Low Side Reverse Protection Diode + Wide Battery Input Range

Quick background: I'm working on a very wide input range for a battery powered application (capability for two different types of chemistries). In the original design, a low side NFET was used as ...
0
votes
1answer
61 views

Is it possible for a voltage multiplier to be used to provide both positive and negative voltage?

What I was wondering is it is possible to use a single voltage multiplier to provide a negative and positive voltage. Referring to this voltage doubler circuit, if you connect a capacitor to the top ...
2
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3answers
227 views

How to find Voltage based on reference nodes?

I came across this problem and I'm trying to really understand it. VB is the voltage drop across a particular element, it is the change in voltage from node a to node b. Find the value of VB in ...
2
votes
2answers
265 views

How do I calculate the diode parameters for reverse polarity protection?

I understand that a diode allows current to flow in one direction only, and that inserting a diode in series with a power source will protect the circuit from a reverse polarity battery. How do I ...
0
votes
1answer
53 views

High Side Driver IC - Application Information

I have a question regarding VN5025AJ-E: High side driver IC. Datasheet link - https://www.st.com/resource/en/datasheet/vn5025aj-e.pdf In the figure you can see the application schematic. In the ...
1
vote
3answers
325 views

Reversing USB power polarity, but no black wire

My goal is to create a USB-to-USB cable with reversed polarity in order to charge an old Gameboy Advanced SP. I could just go on Amazon and buy a charging cable, but I do enjoy a fun little project ...
0
votes
1answer
147 views

What part of a mobile phone charger makes it safe to be charged with opposites polarity? [closed]

A mobile phone charger works regardless of whether the charger is the right side up or upside down. As I know, batteries should not be charged with wrong polarity. How do those chargers accomplish ...
0
votes
1answer
51 views

How to deal with extra pins on reversible connectors?

I want a header on my board to be reversible. The header has 4 UARTs, 4 power pins (VA,VB,VC,VD), and power (3V3) and PWM for a servo. The functions of most of the signal pins of the header are ...
0
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0answers
121 views

NMOS Gate RC Filter Values

I am designing a Reverse Polarity Protection circuit for a project by using an n-channel MOSFET. A basic schematic is shown here. I've added an RC filter so that the voltage on the Gate pin changes ...
1
vote
1answer
133 views

Protecting against reverse polarity

I'm building a JTAG programmer for the old Motorola 56k devices and I want to add some circuit protection before having some boards built. I'm more of a firmware/digital guy, but here's what I came up ...
0
votes
2answers
217 views

Protecting microcontroller digital output pin from ESD, reverse connection, and other possible user error

I want to protect an output pin from ESD, reverse connection, and other possible user error that might cause damages to my circuit. This pin output pulses depend on the amount of water passing through ...
2
votes
1answer
297 views

P-MOSFET allowed some reverse current, L7805CV destroyed. Why?

I was experimenting with reverse voltage protection using a P-channel MOSFET. I hooked up an IRF9510PBF in the following configuration (diagram from Nick Gammon's site, will change if requested): ...
0
votes
1answer
140 views

Circuit Testing failed (Reverse polarity and Buck-Converter)

Hello guys, today I tested my circuit. Its a simple Reverse Polarity Protection Circuit with a Buck-Converter. As I supplied voltagae to my circuit, everything was well (3.5V output). Going higher ...
0
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0answers
62 views

How to connect a generator and LED device of different polarities?

I have a device that generates light impulses when connected to a LED device. The intensity of the light is regulated by a potentiometer, within the generator. There are 2 independent channels. The ...
0
votes
1answer
380 views

How should I go about protecting a supercapacitor from reverse polarity?

I have several supercapacitors in series, and they're quite old and probably drifted from their original spec by quite a bit. Completely draining them in series will draw at least one of them below 0v....
0
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0answers
234 views

Is it possible to connect/disconnect TP4056 using a combination of N and P channel Mosfet?

I'm trying to design a parallel charger for 4 18650 batteries using 4 TP4056. The main idea is to isolate each battery when the "External Power" is connected, so each charging circuit can charge its ...
0
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2answers
168 views

Can I buy an ideal diode? How do I OR two power supplies together

I'm trying to switch over from USB power to external power if it's present. (External power is 6V to 13V). The current is 2A. To do this I'm using diodes 1 and 3. See image below. ("OR" configuration....
0
votes
1answer
287 views

Polarised capacitor - negative voltage?

I designed a circuit that is similar to the circuit on the picture below. The main difference in my design is that I am using a 3V battery and more LEDs. I am using UNPOLARISED capacitors because I ...
0
votes
1answer
352 views

Power supply protection to charge a battery

I am using a power source to charge a battery. To protect the power supply from reverse polarity conection of battery I included a PMOSFET transistor like showed: simulate this circuit – ...
0
votes
3answers
694 views

Is placing a diode in conduction path to ground OK?

Are there any drawbacks to placing a diode in the conduction path to ground for reverse polarity protection? A major plus is cost, because you can use multiple low current diodes, instead of one ...
0
votes
1answer
117 views

How to protect my DIY bench power supply from reverse polarity?

I have been playing with arrays of 18650 batteries for the last 10 months, charging and discharging them all the time with my LM338K based power supply, that, until tonight, where I inadvertently ...
0
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3answers
63 views

Using two switches to each send current in opposite directions

I have two momentary switches, one to activate a solenoid and one to reset it. It is only possible to press zero or one of the two switches at the same time. Using a single battery, how can I wire the ...
3
votes
1answer
772 views

A question about preventing reverse polarity for supply rails of an opamp

Below is an example circuit: I have some circuits based on opamps similar to the ones above. I want to prevent a situation if one powers supply rails Vcc and Vee reverse way. Normally this would ...
4
votes
2answers
409 views

Switching power supply reverse driving protection circuit

I have already "designed" (more like followed the reference design from TI) a buck regulator based on the LM3671 (https://github.com/volium/PowerSupply_lm3671) and I've been very happy with the ...
0
votes
1answer
289 views

How to reverse polarity on only one device?

I have a temperature controller with two SPST relay contacts, one each for heating and cooling, and I want to use them to control a Peltier thermoelectric cooler (TEC), plus a fan and pump and ...
2
votes
1answer
318 views

LM741 op-amp, converting positive output to negative

I've got a few LM741 op-amps that I purchased by accident months ago, but now I'm in a situation where I believe they may be useful. What I want to do is convert a positive voltage to the exact equal ...
1
vote
2answers
86 views

A DC source and only a Reverse Diode

What will happen having only a DC source and a diode connected in reverse? Will the diode or the source overheat over time or something bad might happen if you let it operate like that?
0
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3answers
171 views

What role does this diode play in this reverse voltage protector circuit?

I have been trying to understand this schematic, which is I believe intended to be provide reverse voltage protection. I understand most of the aspects of this. The basic idea is that D3 allows ...
-4
votes
2answers
659 views

How does electrolytic capacitors work?

Basically I am interested about the polarity of an electrolytic capacitor.How is the polarity of an electrolytic capacitor is defined and what if I reverse the polarity in a simple circuit containing ...
0
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4answers
337 views

Feasibility of reverse polarity feature

If I were to design a circuit for a small appliance that works in DC and I would want to allow it to work with the batteries in reverse polarity could I feasibly use a diode bridge? Would it make ...
1
vote
3answers
108 views

night day circuit voltage drop

I found this circuit on internet looking for a "ON when dark/OFF when light" circuit: When I mounted it, it worked as expected, the only problem is that voltage between A and B is 8.71v instead of ...
0
votes
1answer
65 views

Help me correct this circuit with N mosfet

I am trying to build a protection for my circuit in case someone attached batteries or any power supply in reverse even if the other supply is normally attached. As you can see I have 2 power ...
2
votes
2answers
772 views

What will reverse polarity in an Energizer AAA, unpowered, dead battery, circuit?

Circuit is a three-LED reading lamp. Batteries were left in for "a long time, but it worked last time I used it" according to Mom. Unknown if switch was 0 or 1. All three batteries were inserted ...
0
votes
0answers
83 views

Reverse polarity protection non-isolated power supply

I'm trying to design a circuit with reverse polarity protection. I have found numerous of examples but I can't get it to work for me with a non-isolated power supply. I'm open for suggestions. I ...