Questions tagged [automotive]

Questions about the design of electronics for use in an automotive environment. (Questions about the installation and use of automotive electronics are unlikely to be appropriate for this site.)

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11 votes
2 answers
17k views

How do I protect against an automotive load dump?

A load dump occurs when the load to which a generator is delivering current is abruptly disconnected. In automotive electronics, this applies to disconnecting a battery while it is being charged by ...
tyblu's user avatar
  • 8,207
8 votes
4 answers
22k 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 ...
StealthRT's user avatar
  • 741
101 votes
10 answers
320k views

Why does a Tesla car use an AC motor instead of a DC one?

I was just watching a mega factory video and wondered why they use an AC motor which requires a power inverter instead of DC which may be powered directly from their DC battery? Introducing an ...
wizzup's user avatar
  • 1,121
15 votes
4 answers
6k views

Protection against automotive power supply hazards

I'm looking for a way to protect a small circuit which is to be used inside of a car or truck (12V or 24V power system). The circuit consumes about 12-15W. I use an isolated DC/DC converter module ...
Nico Erfurth's user avatar
3 votes
3 answers
3k views

Car bluetooth power delay- USB capacitor? [closed]

I just bought a bluetooth adapter for my car. It's input is 5V/0.3A and is powered via a 5V/1A USB power adaptor that is plugged into the 12V/10A/120W max. socket in the center console of my 2004 ...
Minty_Tiger's user avatar
2 votes
3 answers
19k views

How to calculate bus load of CAN bus?

I have a few questions regarding CAN bus load Is there any derived equation/formula to calculate the bus load? I need transmit below frames(Assume Standard frame format) at baud rate 500 kbps on the ...
Siva babu Rai's user avatar
4 votes
4 answers
10k views

Combining RFID badges

I have multiple RFID cards that I use to get into parking garages at the office, client site, home, parents place, etc, etc, etc..... I'd like to either A) combine all of these into 1 card or ...
coergo's user avatar
  • 41
65 votes
8 answers
20k views

Why are there so many relays used in a car, instead of transistors?

Recently I did some work on my car electric circuits. I see many relays are used in car circuits. These relays are used for simple switching, and I wonder why these circuits are based on relays and ...
Al Kepp's user avatar
  • 2,991
48 votes
3 answers
247k views

Why do we connect a battery to ground when jumping a car?

This may seem like a very simple question, but I've searched all over the place and haven't found an answer. When jumping a car, we connect the + end of the charged battery to the + end of the dead ...
Ken Levinski's user avatar
27 votes
1 answer
172k views

What is the polarity of a car cigarette lighter adapter?

There is a center pin, and two outside tabs. Which are positive and negative?
Mark Harrison's user avatar
18 votes
3 answers
3k views

What does an EV "wall socket charging cable" do?

Known as "Mode 2 charging", this method of charging electric vehicles describes the use of a common household wall socket and common mains voltage (230 v) to charge the vehicle. This is ...
hadrox's user avatar
  • 323
17 votes
4 answers
50k views

Using LiFePO4 battery as car battery

I've had an idea of using LiFePO4 battery as replacement for car battery, since 4 of those in series make nominal 12.8V which is very close to standard 12V voltage. And depending on the cell we can ...
ozzo's user avatar
  • 185
6 votes
1 answer
25k views

Why is there risk of overvoltage when jump-starting a vehicle?

Ford Focus C-Max manual describes jump-starting procedure as follows: shut off everything, connect the jump cables, start the donor vehicle engine and let it run for a while, turn the ignition key on ...
sharptooth's user avatar
  • 12.4k
6 votes
2 answers
4k views

Automotive electrical system. How does everything work?

I recently grew a big interest into the electronic world. I also love auto/mechanics, and I’m trying to understand where these two wonderful areas meet. I’m trying to understand the fundamentals of ...
amalik's user avatar
  • 69
5 votes
2 answers
10k views

Why do PTC fuses have different voltage ratings depending on package size / hold current?

I've been trying to figure out the PTC fuse I want to use in a little automotive power supply circuit and I'm a little disconcerted by the max Vdc ratings most of these things have. For instance, ...
Toby Lawrence's user avatar
3 votes
2 answers
359 views

Automotive electronic circuit design: voltage divider to uC ADC pin

Automotive circuit requirement: If input pin is connected to Battery(T87 line), the output of the circuit shall provide a output voltage of 5V to ADC pin of microcontroller, if the input pin is ...
Nidhi's user avatar
  • 87
2 votes
2 answers
2k views

Do fuse blow on ampere or effect?

I have a faulty car (bad central locking engines) and a fuse is blowing every time I open/lock the it. I'm looking to do a quick fix, and just replace it with an automatic fuse. The car runs on ~12V, ...
Dog eat cat world's user avatar
2 votes
2 answers
1k views

What would happen if I choose a connector with current rating smaller than the actual current?

I need a butt splice connector that can handle up to 150A, which is really hard to find. What would happen if I connect it to a 12-10AWG butt splice connector? Other type of connectors are not ...
Le Hoang Long's user avatar
1 vote
1 answer
276 views

Which cell balancing method (active or passive) is best for low-voltage BMS (Battery Management System)?

As a beginner, I am going to design and develop a BMS (Battery Management System) for low-voltage applications (electric bike). So I would like to know which cell balancing method is perfect for low-...
Muthu's user avatar
  • 577
0 votes
2 answers
3k views

Sense Automotive 12V Circuit from 3.3V microcontroller safely

I want to sense a circuit state in an Automotive circuit (12V nominal) from a 3.3V microcontroller (MSP430Gxxxx). The circuit is normally 12V (or VBat) until either the Wireless ECU or a Door Key ...
Passerby's user avatar
  • 72.9k
0 votes
1 answer
1k views

current/voltage isolators in cars

When I attach something sensitive like a analog camera and LCD screen to a car battery along with a switched high amp load like a power door lock actuator, I get video problems when the load is ...
Arewfawe Waefadffawe's user avatar
86 votes
6 answers
12k views

Will radar/lidar still work when every car is equipped with them?

Self driving cars rely on cameras, radar, and lidar to recognize the environment around them. Cameras of course don't interfere with each other, since they are passive sensors. Since a signal ...
crj11's user avatar
  • 5,556
22 votes
9 answers
103k views

Why is the chassis used as ground in automotive electrical circuits

Automotive electronics generally use the metal chassis as the negative ground connector for the DC circuits. Obviously this saves something on wiring. Is there an electrical reason for this approach? ...
bib's user avatar
  • 323
20 votes
7 answers
4k views

Is "automotive" grade always better?

I'm working on the parts list for a number of designs for low-voltage (24 VDC) industrial circuits that have no special safety requirements: so long as they don't catch fire no one could be hurt nor ...
jonathanjo's user avatar
  • 13.9k
19 votes
5 answers
15k views

Tesla Car "maximum torque at 0 RPM" - is this correct?

Tesla Model S Wiki I've been watching youtube videos on this car, and everyone states that the crazy accelleration is due to maximum torque at 0 rpm. Doing further research, this car uses an AC ...
tgun926's user avatar
  • 2,766
15 votes
3 answers
8k views

Arduino in car: capacitor for extra 3 sec of power

I want to install an Arduino Uno in a car, powered by a consumer 12V->5V car voltage regulator plugged into the lighter socket. The socket is switched, i.e, there's no power when the motor's off. When ...
MrSparkly's user avatar
  • 253
13 votes
2 answers
3k views

Simulating an automotive load dump with a bank of charged capacitors?

I've been working on a data logging device that will eventually go into my personal vehicle. I've scoured the interwebs and built what, in theory, should be a fairly stout power supply capable to ...
Toby Lawrence's user avatar
9 votes
1 answer
3k views

How can I simulate and handle an automotive load dump?

Long story short, I'm designing a little device to monitor a sensor or two in my car. I'm not an EE, but I'm a stickler for knowing things will work right and that I won't have wasted my time and ...
Toby Lawrence's user avatar
9 votes
3 answers
24k views

Splitting wires for newbies

I'm in the process of getting ready to build a car PC running Linux. One of the features I'd really like to incorporate is the ability to record car statistics from the sensors live using ODB2. Due ...
Naftuli Kay's user avatar
9 votes
2 answers
4k views

Automotive power filtering, protection - feedback needed

I'm working on GPS tracker for automotive applications. Device should work in 9V-30V supply voltage range. In practice it will be fed from 12V car installation. This enforces the implementation of ...
Krzysztof's user avatar
  • 258
9 votes
1 answer
3k views

In terms of protection, how does this automotive power supply circuit look?

Preface This is a power supply circuit I designed that will be part of a larger device. The very basic intention is that it will take standard +12V automotive power and generate a 5V output and 3....
Toby Lawrence's user avatar
6 votes
3 answers
62k views

Is it okay to keep a USB charger plugged into the cigar lighter?

I have a USB micro charging adapter for my smartphone for my car. It is basically a cigar lighter plug that turns into a USB micro plug. When I don’t have my phone connected, and as such don’t want ...
poke's user avatar
  • 165
6 votes
5 answers
21k views

CAN Bus Physical Layer Twisted pair or not

CAN bus is very common in automotive or vehicular applications. In our case, we are using aerial platforms with have CAN bus links between operator remote and ground control box. As is very typical ...
Philibert Perusse's user avatar
5 votes
4 answers
862 views

Does anybody recognize this automotive connector?

I'm trying to repair a wiring harness, and I'd rather pin and install a connector than splice into a junkyard pigtail. Does anyone recognize this and know where to find them? There's some serious ...
Bryan Boettcher's user avatar
5 votes
1 answer
2k views

Converting a tachometer signal into something a microprocessor can understand

I am attempting to build a digital dashboard for my car (a 1998 honda civic), I have run into a bit of trouble, wherein the tachometer signal is quite hairy. I was wondering if someone would lend me a ...
Patrick's user avatar
  • 206
5 votes
4 answers
503 views

Industrial electronics layout and design

Why do industrial panels for oil and natural gas compressors or other industrial equipment use terminal blocks for wire management? I have been doing some repairs for companies and was wondering why ...
longjohnmcgee's user avatar
5 votes
4 answers
4k views

Checking when a car horn is pressed?

I want to detect when a car horn is pressed. The only way I can detect it currently is using the voltage on its line. When the car is turned on, there is always 12V being supplied to the horn through ...
prog_SAHIL's user avatar
4 votes
1 answer
2k views

How can CAN transceivers ouput CANH=3.5V and CANL=1.5V?

When sending a dominant bit (0bit) on the CAN bus, I understand that CAN transceivers output CANH=3.5V and CANL=1.5V. But when looking at the schematics of a CAN transceiver, I do not understand how ...
Kyong Tak Cho's user avatar
4 votes
3 answers
2k views

Automotive Load Dump Protection Circuit

Currently I'm working on a project that will be implemented in a 12V automotive electrical system. To protect the onboard DC/DC, I decided to add reverse polarity protection as well as load dump ...
mke's user avatar
  • 53
3 votes
2 answers
10k 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/...
unix's user avatar
  • 183
3 votes
2 answers
674 views

Possible to reliably run USB over a non-standard USB cable?

I'm planning on building a device for my car that sits somewhere in the rain tray or behind the dashboard. It will use automotive connectors so that things are sealed, easily connected and ...
Toby Lawrence's user avatar
3 votes
1 answer
1k views

Switch from electolytic to ceramic capacitors in car ECU?

I'm looking into replacing the capacitors in the vehicles ECU. I know the ratings and voltages for the three. My question though is which would be better to go with, electrolytic or ceramic. I'm not ...
OMEGA_RAZER's user avatar
3 votes
1 answer
2k views

DIY Aux In connection to car stereo JVC KD-G151

I would like to connect my phone via jack cable (aux in) to my car stereo, which has no aux input (brand: JVC KD-G151). It is a CD player, so i wrote a silent disk to operate the cd player, and tried ...
davidszasz91's user avatar
3 votes
2 answers
7k views

OBD port power source [closed]

I've read on forums that OBD port can provide max 5A current at 12V. What is the source of the power? Is it coming from battery directly or is it regulated power supply from somewhere else, maybe ECU? ...
Lalit Kumar's user avatar
3 votes
7 answers
3k views

Opinions on what I've come up with for a 12 V-to-5 V automotive circuit?

Is this a solid solution for an automotive 12 V-to-5 V circuit to power an ATtiny? I've been trying to come up with a solution for my needs that can handle the automotive environment that is so scary ...
dawm's user avatar
  • 59
2 votes
4 answers
6k views

Alternator current when charging flat battery

I've found some voltage-current-rpm graphs for car alternators and did not quite understand one thing. Basically, my alternator is rated at 75A (small car), which it should output above 2000 RPM or so....
elektrinis's user avatar
2 votes
1 answer
325 views

Powering Atmega, DAC and Bluetooth in Car

I'm looking for a proper power supply schematic which would fit my needs and would have all required protections (overcurrent, overvoltage, reverse current, etc) for use in car. I want to power Atmega ...
user1258202's user avatar
2 votes
2 answers
1k views

Automobile Project (Electrical Parts Requirement)

I'm looking at putting together a circuit board to be used in an automobile. It will only be connected to a 12 V and ground. Everything else will be internal to my board. I was planning on putting a ...
user16105's user avatar
  • 171
2 votes
1 answer
7k views

Jump start car from lithium ion laptop battery

Building the actual circuits is beyond me at this point, but I'm wondering if it's technically possible to jump start a car from the power contained in a large lithium-ion laptop battery. For example,...
Lessac's user avatar
  • 123
2 votes
2 answers
4k views

Reverse Polarity & Load Dump Protection (TVS)

Based on this and other material I’ve read, I should have a diode for reverse polarity protection and a TVS for load-dump protection in an automotive circuit. I have prototyped the circuit and its ...
unix's user avatar
  • 183