# Questions tagged [12v]

Questions relating systems powered by a 12 volt supply. This may include automotive systems and lead-acid batteries that are nominally 12 volts although be aware that under many conditions the actual voltage may be several volts higher.

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### Can a 12V battery give you a shock or not?

I am reading a book called "Make: Electronics" and, on page 9, it says: "Anyone who has dropped an adjustable wrench across the bare terminals of a car battery will tell you that short circuits can ...
80k views

### How to transform 5V into 12V?

I would like to transform 5V 500mA (from USB power) into 12V with a few cheap components. Is this possible with the help of some generic parts (and not with the help of some expensive transformer, ...
4k views

### Explain the logic of a 12 V to 9 V conversion

How does the below circuit work? I know what resistors, capacitors, and transistors do and have played with them on a microcontroller board, but am I trying to understand the logic of the circuit. I ...
75k views

### Using a 12V battery while simultaneously charging via solar panel

I have a couple of 12v batteries that I'd like to use to power a cooling apparatus while camping for several days. I also have a 15W solar panel I'd like to use to top-off the battery. Can I use the ...
6k views

### 12 V car battery short circuit with a wrench that has resistance of 0.5 ohms, how much current?

ANSWER/ERROR FOUND: resistance of the leads of the multi-meter is the culprit. The true resistance of the wrench cannot be measured using a basic multimeter. The resistance of the wrench is more so ...
2k views

### Using a 12 V 3 A bilge pump on a 12 V 8.5 A LED power supply

I recently bought the following for a grey water system project I'm working on: 3 x 12 V, 3 A bilge pumps 1 x 12 V 12.5 A power supply I'm not an electronics expert, so my assumption was that the ...
1k views

### Is there a way to tell what frequency I need a PWM to be?

I have a 12V DC motor that turns at 60 RPMs or 1 Hz. Do I need a PWM that matches the frequency in order for it to work? Most of the ones I've seen are around 25 kHz for a 12V 20A motor.
18k views

### Switching 12V with an active low 5V signal

I’m trying to switch 12V (max 30mA) with a signal from a MCU that I’d prefer to be active low (so the output voltage is 12V when the control signal is 0V, and 0V when the control signal is 5V). Since ...
2k views

### How to make -12V from a +12V supply?

The equipment I have needs +5V +12V and -12V supplied to it. The old PSU which provided all the voltages blew to bits. I have sourced a PSU1 +5V (30A), and PSU2 &PSU3 (two identical +12V (2A) ...
13k views

### Replacing incandescent bulbs with LEDs, unexpected behavior

I have an over-the-stove microwave/ hood vent combo with 2 adjustable-brightness lights. The lights appear to be 12V lamps with a G4-style connector, and they burn out all the time... like every 4 or ...
2k views

### DIY 12 Volt UPS

Hi i am trying to make a UPS for a project that requires 12Volts. I'm currently using a replay diode and capacitor. My problem is that when the switchover occurs, the voltage drops from 12Volts to ...
6k views

### Arduino Uno with 12V pump: transistor or optocoupler+12V relay?

I'm not a real expert in electronics but I'm going to start a new project that has completely captured me. I need to drive a 12V pump with my Arduino Uno. The pump is "Dp0102" (12V, 0.7A). To power ...
16k views

### Detect car +12V using Arduino

I am looking to detect 12+V from a car wire using an Arduino. I have found the following schematic: I know how crazy automotive voltage can get so I just want to make sure the schematic I found ...
1k views

### Discharge time of 12 V 8.4 Ah at 5 mA

I have a motorcycle battery rated as 8.4 Ah (20 HR). It also says 8 Ah (10 HR) and I am not sure what the difference is. Anyway, I have a GPS tracker fitted with a rated ...
4k views

### What are the standard connectors used on 12V hobby batteries?

I'm looking for a right-angle PCB board mate for the standard 12V hobby battery connectors. Where can I find these connectors?
2k views

### picking a FET for 12v use with Arduino

I am working on an Arduino project where I would like to use an output pin to control a 12v load with a mosfet. I think it should be an n-fet, but am not sure. I have been looking at specs, and don'...
29k views

### How can I safely charge 3 lithium 18650 batteries to use in one pack?

I'm working on a project to make my own super-bright bike taillight using an emergency flasher LED (something like this:) The LED package requires a 12V input, but from what I've read from other ...
18k views

### How can I model a relay in LTSpice IV?

I would like to use a 12V relay in my LTspice circuit, however there is no relay in the component list. How can I do? Relay model: SRD-12VDC-SL-C
2k views

### Implementing powerline communication on a battery-fed 12V line

I was wondering if anybody had any thoughts on whether it is possible to implement powerline communication on a lead-acid battery fed-12V power network. Characteristics: voltage: 12 V Fed by a ...
4k views

### read 12V logic pin from arduino using an NPN transistor

I have an inductance sensor on a CNC machine that goes 12V high when triggered (open collector when not) . I want to read that input on my arduino who uses 5V logic. I was thinking I could just use a ...
42k views

### How long will it take to completely run out of power for two A23 batties(12volt each) on a serial circuit with 6 leds?

I'm connecting 6 LEDs serially with two 12volt batteries. Each LED needs 3.2 volt and takes 20mA of current. I'm using two alkaline max 12 volt batteries(A23 LR23) and ATC is their manufacturer. I ...
19k views

### 12V LED strips in series with a 24V power supply?

I am purchasing 50x - 1Meter / 12V / 72 LED /Rigid SMD 5730 strips directly from china. I don't know the LED manufacturer, nor the resistor being used. (yes, this is a gamble) The strip is one that ...
391 views

### Finding a 12 V Peltier module that reaches less than 0 °C on the cold side

I am making a small cooler box using a Peltier. At first, I used a Tec1-12706 without researching first, and it barely went under 12 °C at the cold side. I need a Peltier module that is 40 mm x 40 mm ...
854 views

### -12v power source for op-amp

I plan on building this buffer circuit to use my sound card as an oscilloscope, but I’m not sure on the best/acceptable way to get the -12V. Can I use a 24V DC power supply and then use a voltage ...
7k views

### Generating 12V PWM from 5V PWM

I am generating a 5V PWM signal from my MCU (an Atmel ATMEGA1284P). I need to convert this to a 12V PWM signal. For this I designed the circuit below, something very similar to a Sziklai pair, but ...
758 views

### Netduino to power 12V LED Strip

I'm a programmer by nature, but I thought I'd try dabbling in programming a micro controller. I've hooked up my voltage meter, and have figured out how to switch my output ports on/off, and they're ...
7k views

### Connecting Voltage Regulators 7812 in Parallel for High Current [duplicate]

Could I use two L7812 voltage regulator ICs in parallel to get 12 volt and more current that with just one?
697 views

### 12V lead acid charger with LM317 not charging

I have this circuit built and tested. I think this should work and charge the battery with 0.4A to about 13.5V. The Problem: it doesn't charge and between U1 and U3 (Battery) is a current of about 0....
4k views

### Will 16-20 1.5 volt serially connected led lights tolerate 12volt energizer battery source?

I am doing a little project with 1.5volt led lights. I want to buy 16-20 1.5volt led lights and connect them serially and need advice on power source. If I connect these serially connected led lights ...
2k views

### Data over power line in a car

I am trying to build a communications system for a car, for turning gadgets on or off. One idea was to parasite on power lines, but what kind of components and signaling could be used for this? I am ...
3k views

### Can I get 24V from ATX PSU using 12V and -12V cables?

ATX PSU's have one -12V cable, and a few 12V yellow ones. Could I power up a 24V device by connecting 12V to + on the device and -12V on -?
11k views

### I’d like the 12v rocker switch LED to illuminate when the switch is turn OFF

I've exhausted a google search and am hopeful expertise on this board can help me with my objective. My Arcade has LED lighted buttons when the cabinet is on. The LED button lights are powered by a ...
4k views

### Low Voltage DC Automatic Transfer Switch

I am new to circuits and have a very basic knowledge, and am currently interested in building a simple circuit that would take 2 DC inputs each of 12V 1.5A and output 1 x 12V 1.5A input even if 1 of ...
12k views

### Clean 12v car power

I am looking to get a constant, clean 12V from my cars 12V line. I am wondering if all I am in need of to pull this off would be a simple 12V fixed regulator? The 12V would be hooked up to a pico ...
132 views

### Motorbike turn-signal blinker starts OFF, I want it start ON

I bought a cheap blinker that claims to be good for LED bulbs (so the frequency is independent of the load.) It is true, but it has a flaw: the lamps go ON only after about a half second from when I ...
1k views

### How to compensate voltage drop on a wire

I'm using a 12v power supply with 12 meter cable ( 0.5mm ) to feed 4 small motors that use around 3A. My problem is that when I turn all the motors the voltage goes to 7 volts. I need it t stay ...
950 views

### Why is this switching transistor heating up?

I am building control board for fan cooling. It runs from 12V power source, and it is controlled by input analog signal 0.3V to 1.2V which just controls speed of fan. Problem is that switching ...
6k views

### Replacing alternator warning lamp with LED

I have an alternator on an in-board motor in a boat, I have almost completed re-wiring the electrical system and am wondering if it is possible to replace the existing filament lamp. I have ...
9k views

### Led strip dimming

I have a problem with my led strip starting to flicker/flash when I send a low pwm signal from my arduino (analogWrite 1-79). Here's a video: https://www.youtube.com/watch?v=X8wHzEQ4Wvw I'm using a ...
260 views

### How long can I run my camera off this battery?

I have Ultramax NP7-12 12v 7ah specifications here: http://www.batterymasters.co.uk/ProductDocs/SLAUMXNP7-12-TECH.pdf My camera consumes 1.25 watts per hour and runs at 7.8 volts but can run between ...
598 views

### How will the output of a 12V transformer wall wart differ from that of a 12V SMPS brick?

I have been working on a project to drive an electric door strike from an Arduino shield of my own design. Actually, I'm using a Freetronics Eleven and not an official Arduino, which is relevant ...
5k views

### Relay for Intermittent Wiper Function

I want to add an intermittent function to the wipers on my 40-year-old car without any additional switches. The details of the wipers can be found here [http://www.globalsoftware-inc.com/coolerman/...
572 views

### Get 12v power from NiMH battery

I have an Arduino project that is powered from 12v/15A dc power source needs to switch to battery power and still get 12v (dc power may start/stop at any time) recharge the battery when dc power ...
11k views

### Making 12V DC from 6V AC

I've got a 1980 Honda XL 185s that has a 6 volt electrical system. The headlight uses a 6V AC, 30 watt bulb powered from the generator. The other lights (tail, blinkers) operate off of the 6 volt ...
560 views

### Is Automobile Power Viable for Electronics Projects?

I have some project ideas that would be targetted for use in a vehicle. I would like to consider the possibility of tapping into the car's 12V battery to power the projects, for example through the ...
18k views

### Xbox one power adapter wiring - converting it to a 12 volt power supply

Thanks for having a look at my question. I know this may seem like an odd question but here is the history of it. I have a Solidoodle 4 3D printer, Its powered by a knock off xbox 360 brick adapter ...
4k views

### Control of 4 pin cpu fan with 3 pin socket and …?

I have a problem with controlling my cpu fan speed since it has a 4 pin connector and the socket on my motherboard is broken (transistor connected to it has burnt). I have it connect at the moment ...
1k views

### Solar MPPT charger causing regular voltage spikes

I have a van which has two 12V solar panels on the roof. The charger is connected to the batteries and seems to constantly be outputting about 13v. I've had it installed for a couple of days and I'...