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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2
votes
2answers
95 views

+5V and -5V power supply from 12V DC

I'm creating an RGB switcher for a car video system and would like to use the MAX466 chip, which needs -5V, GND and +5V. I have no idea how to change normal 12V DC (car battery) to dual 5V. I found ...
0
votes
1answer
63 views

Designing power supply with 5v and 3.3v from a 12v supply with switching regulators

I have 12V DC coming in from a power brick and I need to supply 5V @ 1A for USB and 3.3V @ 5A max for mSata and PCIe. I basically need to make a small atx power supply that I can integrate on my ...
0
votes
2answers
71 views

Automatic 12V plant watering system?

I'm planning to make a plant watering system . There is a beeper so it will alert us when the soil is dry.I have got a 12V DC motor . So i'll be removing this beeper and i need to add this DC ...
0
votes
1answer
81 views

Transistor shortcut

i would like to fade an led strip using pwm with a n mosfet led that is commanded by a two way switch ( relay and sw1 ) like this: simulate this circuit – Schematic created using ...
2
votes
2answers
230 views

Is this 12 volt LED circuit correct?

I found this "Plant Grow LED light" circuit on the Internet and I wanted to know if: (Please don't feel pressured to answer all my questions. You can just answer a few only if you like.) this is ...
2
votes
2answers
70 views

How to allow only 12v

I am looking to control a 12v LED light off of a zwave appliance module. Here is my issue, the zwave module outputs about a 5v pulse every few seconds while in the off state, which is enough to ...
0
votes
1answer
60 views

Rewiring a 12V charger

I have a Windows tablet with a charger which crapped out. The old charger was 12V / 1.5A - fairly standard but it had a rare tiny pin connector. Rather than buy a new charger, I decided to cannibalise ...
0
votes
3answers
134 views

Potentiometer - How?

I bought a 5m LED strip from Ebay and connected it to 12V 1.5Amps. I am a starter in engineering. What kind of potentiometer do I need to use to lower or increase the brightness? How many Ohms do I ...
1
vote
2answers
238 views

Transistors to switch 12V 2A

I need to switch some power to a device, so I was wondering, if this will work OK, or do I need to add some other stuff to protect it, or make it work correctly. I ran some simulations, on ...
0
votes
2answers
66 views

#2 L7809CV regulators, connected to #2 9vdc motors

I simply want to connect 2 motors as i show in the image, using a 12VDC power source and 2 #L7809CV, right now the circuit is this you can see in the image i made. The GND its the same source for ...
0
votes
2answers
86 views

Circuit Requirements for a 30 min continuous on off cycle

I would like to build a circuit (preferably using components from old common electronics like a VCR or whatever) that continuously cycles on/off in ~ 30 min intervals. Input voltage is from a 12v ...
0
votes
1answer
51 views

How Does Connecting a Battery in Series Affect Current Flow

Background: I am creating a circuit to run electronics and motors. The some of the electronics are 5V some are 12V and the motors are 24V. I have a small universal 12V battery for the electronics I ...
0
votes
1answer
43 views

mechanical relay output voltage doesn't change

As a followup to my previous question, where a 2222 npn transistor wasn't beefy enough to handle the load I was putting on it to activate a solenoid valve, I decided to try a mechanical relay board ...
0
votes
2answers
60 views

transistor toggles an LED, but not a solenoid valve

I'm working on a hobby project where I'm trying to drive a solenoid valve with an arduino (for some automated plant watering). The solenoid valve takes 12v, so I've rigged up some smaller batteries ...
0
votes
1answer
68 views

momentary to on/off switch for 12v

I got some oem switches and I want to mod them into light switches. Here is my situation: I would like to use the oem switch since it has illumination and button that matches the car.I have already ...
0
votes
1answer
44 views

electronics voltage sensitivity

I have a 12v battery directly powering a handful of electronic devices (router, modem, hard drives). These vary from 0.5a~2a so I have breakers on the (+) lines ...
0
votes
1answer
52 views

What kind of time delay switch to choose to reverse motor for just a couple of seconds

I would like to know the following: I have a motor driving a lead screw which transports a part either up or down. When going down and something comes in the way a switch gets triggered by the ...
0
votes
1answer
82 views

Running a load off a solar panel connected to 2x 12V batteries.

I am having trouble figuring out what relay I should be using for my solar panel set up. I have a solar panel running to a solar charge controller. I then have the controller running into a relay. ...
0
votes
3answers
133 views

How to measure amperate going through a 220V cable?

Meta objective: I want to pull up a TV with a winch, when the TV is turned off. I can already move up and down the TV invoked by my controller (Arduino Nano). The physical push-sensor stops the winch ...
0
votes
0answers
123 views

Custom USB 7 port hub PCB dasiy-chain

I had a schematic laid out for a custom USB 2.0 7-port hub I needed to create for a project of mine. It currently uses Ethernet RJ45 sockets to provide power and data to each hub (2 Ethernet ports for ...
-2
votes
1answer
67 views

Can a 12v 27a alkaline battery damage? [closed]

I've looked inside my garage remote control and I've discovered a 12v 27a battery. The voltage is very low, but the ampere are many, can it damage a person when is fully charged? Thanks
1
vote
1answer
149 views

How to wire multiple 2 volt flickering LEDs to work on 12V auto system

I have tried to use the site to find an answer to this, but it seems everyone that has asked questions have different variables than I am dealing with, and I can't ever seem to grasp electrical ...
-2
votes
1answer
119 views

Connecting two power supplies with almost like voltages to an amplifier in parallel

I have recently been working on a custom sound system in my living room. For the subwoofer, I am using a 1000W amplifier. This is currently running off of a 12V computer power supply that outputs ...
3
votes
1answer
82 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 ...
0
votes
0answers
42 views

Emulating, tricking or faking a liquid cooling sensor

I have a specialty server board with an attached liquid cooling system, the liquid cooler has 3 pins attached to the board, pin 1 gnd, pin 2 12v+, pin3 sense. I'm assuiming this works like a cpu fan. ...
0
votes
1answer
86 views

Clock / timer activated 2 second voltage timer for wiper motor project

Ok, I need a 12 volt voltage timer using clock or timer for a wiper motor. I am working on a project in my garage. Simply put, I am wanting to use a wiper motor that will open and close a spring held ...
1
vote
2answers
514 views

Two relays for DRL on a car

I am trying to make a circuit for my newly installed DRL (Day running lights), what I am trying to do is have the DRL run all the time, turn off when using high beam, dimmed when headlights are on. I ...
2
votes
2answers
95 views

Interfacing incompletely documented logic signal where resistor affects output voltage level

So I've got this marginally documented 12V logic signal from something I have to regard as a black box that I'd like to interface to a pi or arduino (i.e. c 3V). I have 3 lines - 0V, +12V and signal ...
0
votes
1answer
98 views

electrical fridge running on car battery [closed]

I'll be out of grid for some days and I'm planning to have a small electrical fridge with me. It's a 12V 4A small fridge with a cigar lighter plug, but I won't have a car with me, so I think I could ...
1
vote
1answer
1k 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 ...
-3
votes
1answer
49 views

12 v xbox connection [duplicate]

Hi again if I just want to connect my tv and x box360 to the mains I've got it connected to the van at no so the neg is to the body and pos is by the fuse box. Can I just wire the transformer neg to ...
0
votes
1answer
1k views

How to build a blinking 12V indicator LED light

I attempt to build a blinking circuit using 12V truck light ( like this one: http://www.princessauto.com/pal/en/Tail-Lights/4-in-LED-Stop-Turn-Tail-Light/8126047.p). I have try to build a single LED ...
-1
votes
3answers
123 views

Need to cap voltage at 12V, and need to vary voltage down

I tried to find something like this in the knowledge base, but didn't see a perfect match. I have a small submersible pump. 12VDC, 4.8W. Model DC30a-1230. I assume that is 0.4amps. There seem to ...
1
vote
2answers
157 views

UPS 12V power switching

I was trying to make a sort of UPS circuit with a 12V DC 5Ah power supply and a 12V 5Ah seal-lead battery. My question is that I don't know how to switch quickly from line supply to battery. I've ...
1
vote
2answers
93 views

Messing with rgb leds and have a question

I have some LEDs that I'm wanting to use in a project. I would like to know what's the best resistor I would need to get the most light out of the 3 different colors using a 12v source. I've measured ...
-2
votes
2answers
2k views

Charging battery using computer power supply?

I have new 600W ATX computer power supply unit. I have wired green and black together to make power supply turn on when plugged in. I wanted to charge my 12VDC empty battery, without dealing damage to ...
1
vote
1answer
213 views

Best method to eliminate alternator whine from a 12V line?

I've purchased a Miccus Mini-Jack Rx BlueTooth audio receiver. This device will accept a bluetooth signal from my phone and output it to a headphone jack that I plug into the AUX-In on my car stereo. ...
1
vote
3answers
244 views

Best way to drop 12V fan to 7-9V? [closed]

So my Xbox one PSU died and microsoft doesn't sell official ones yet, so I bought a third party one and the fan that is in it is a 12V blower fan with 2 wires running right to the board (it says 12V ...
0
votes
1answer
181 views

Can I damage a device using opposite polarity? [closed]

I have a device that requires input of 12V DC with positive polarity and a power supply that outputs 12V DC negative polarity (see figures below). Can I plug it in to try to see if it's working or ...
0
votes
4answers
1k views

Why does my DIY “solar panel circuit” show battery voltage and not solar panel voltage?

I've got two solar panels set up in series as shown on the below schema. I connect positive on panel A to positive on battery, and negative on panel B to negative on battery. The two panels produce 9V ...
-1
votes
1answer
147 views

Why does one LED slightly influence the other parallel LED although controled by differenct MOSFET-N?

I created a simple circuit that turns on and off two 12VDC LED with signals from my Arduino Leonardo R3, which is powered by a 5V USB cable from my PC. The LEDs are attached to a dedicated 12V power ...
2
votes
3answers
355 views

Triple output power supply

I need to power my device with three different voltages: 3.3V, 5V and 12V. I already have a 12V 1A power supply. So my questions are: Can I use the circuit below to get these three voltages? Is it ...
1
vote
1answer
58 views

Would this be ok to control the speed of a PC fan? [closed]

I have a 240mm PC fan connected to a 12v adapter. The fan is quite noisy and i would like to have the option to turn the speed up/down or off completely. The Fan is: Current (A): 0.18 The 12v Mains ...
2
votes
2answers
133 views

Can I use this high-side driver with arduino?

I have salvaged a PCB with quite few single and multi-channel high side drivers. One of the is VN5E010AH. If I understood datasheet, this chip can drive high voltage using low voltage cmos compatible ...
1
vote
0answers
64 views

Switching cold cathode fluorescent lights on and off without relay?

I have a few sets of 2-in-1 CCFLs that are designed to be powered off the 12V rail of a computer PSU. I'm planning to build a large 7-seg display using them so I'd like to be able to switch them on ...
6
votes
2answers
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) ...
0
votes
2answers
312 views

How to supply power to a 12V solenoid from China, getting hot

I bought this solenoid from ebay and was wondering how to power it. It says 12 volts as you can also see from the picture, but I tested it with putting a 9V battery straight to its terminals for a ...
1
vote
1answer
793 views

Which diodes for 12v indicator light circuit?

Which diodes for 12v indicator light circuit? I have a car whose signal light audio indicator is too soft to hear. I would like to set-up an visual indicator on the dash for when the signal lights ...
6
votes
1answer
2k 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 ...
0
votes
1answer
108 views

NAND gate from BJTs: interfacing +/- 12v op-amp and 5v logic: destroy BJT with excessive Vebo?

I want to switch on a relay when both a 5v logic input is high and a (LM741 used as a) comparator is around +10v, and the circuit I planned to use is below. The problem I see with the circuit is when ...