# 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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74 views

### Car Battery Voltage

Why is the voltage of a car battery rated for say 12V around 14V when the car is running? Is it because of the alternator?
65 views

### Resistance of car when starting?

A car starter circuit pulls around 500A to start a car. Does this mean the resistance of this circuit is around 12 / 500 = 0.024 ohms? (Assuming the battery is ideal)
564 views

### A kill switch for a car

I want to add a kill switch to my car for the fuel pump relay. The switch I would like to use is one which would need to be pressed/flicked on to start the car but when the car is turned off the power ...
91 views

### Why would touching a rubber insulated spark plug wire causes current to go through your finger?

I'm trying to understand the physics. The spark plug has a gap of 0.9mm. Why would the current go through the insulation resistance, the finger resistance and the air gap between the finger and the ...
32 views

### How to calculate resultant of 32 bit CRCs

Im working on automotive controller and I have following question I have list(about 6) of 32 bit CRCs and I want to combine them to get a resultant one can I 'OR' or 'XOR' them to get resultant one? ...
91 views

### Can you identify this substance on PCB pads?

Can anyone identify what's going on on the PCB pads in the following photo? This is from an automobile ECU that had to be reprogrammed and so was opened and resealed a few days ago. Thermal (silver) ...
155 views

### Will this shottky diode circuit protect my ADC, and if so, are there options with more than 2x channels?

I am trying to read 8x 12VDC digital inputs and 4x 5VDC analog inputs with my 3v3 Teensy 4.0 Microcontroller. In V1 of my design, I used a voltage divider circuit to drop down to 3v3. I would like to ...
79 views

### Which is this component, using in remote car key PCB?

A friend's car key was not working properly, and an electronics repair shop took it to that key. they offered a very high price for the repair and my friend refused and got his key back. Now he ...
47 views

### Is reverse polarity protection required for the ZXTR2005Z regulator?

I am trying to figure out whether reverse polarity protection is required for the ZXTR2005Z regulator. On the one hand, the datasheet is "suspiciously" explicit that the input voltage must ...
46 views

### How to limit pulse duration?

I'm trying to design automotive-oriented circuit to limit ignition pulse duration from OEM ECU to an aftermarket ECU plug-in device. The device expects +12v pulses no longer than 9ms, while the car in ...
60 views

### Electric vehicle instrumentation [closed]

I have converted a vw bus to 112 VDC electric drive (Tesla battery modules 22.5VDC X 5 ea). There is also a 12V system for lights and instruments. The BMS supports SPI and CAN. I have no experience ...
65 views

### How can you power a device using a relay when the device uses power cables to change its operating mode?

I am working on a custom automative install on my car. I have a few lighting fixtures that change colour based on which power +12v wire is being used. For example, each lighting fixture can display a ...
30 views

### Automotive protection: TVS, thermistor, or both?

This is a follow up question regarding my previous post where I was informed my issue was due to inrush current. I have a DC1601B-C buck-boost converter outputting 12V and up to 20 Amps. It is hooked ...
53 views

### DC1601B Demo board input line caught fire during use

I am using a DC1601B-C buck-boost converter in an automotive circuit to power some various electronics that I have added. It worked fine for a couple months, but under a less-than-normal load of 2.25A ...
24 views

### Will USB-PD work with and extension cable in the circuit?

I want to replace the USB type A port on my trucks dash with a USB-C panel mount and give it the ability to "fast charge" my phone. Unless there is a product that I am overlooking it seems I ...
62 views

### Can two EV chargers be combine to increase charging current? [closed]

While charging my EV (Electric Vehicle), Tesla model 3 long range, and watching all the other chargers not being used for the two hours I was there, I wondered if I could use two of them to charge ...
37 views

### Device, Circuit, Component to Manipulate a Relay and an LED Light - Open to Any Ideas

This is my first post, and I am electronically illiterate - have mercy on me.... THE PROBLEM: Dealing with an automotive +12V system - and I have a new voltmeter that I'd like to install. In addition ...
63 views

### Power projector with car inverter [closed]

I have this projector which takes in 19v and has a power consumption of 65 watts. I want to buy a 12v 6A car inveter, that plugs in the cigarette lighter, which would give me 72 watts. The question is ...
157 views

### Zener diode response time

I have the below circuit: Forward diode D0002 - Datasheet SIJ series for reverse protection and C0001-C0004 capacitors for ESD protection. Zener diode - Datasheet - 36V reverse breakdown. Question : ...
43 views

### Composite video from rear car camera - bad signal (wrong levels?)

I have bought a car radio (AMPrime 4022D) that has ability to connect rear camera to it, so you can see the image on its screen. The problem is that radio doesn't detect the signal (blue screen). But ...
39 views

### Making subwoofer for car, without amplifier

So, I have these two things and I want to achive a good subwoofer for my car: an 5.1 home theater system with a 20-30w 4ohm subwoofer and a radio player in my car with 4x45w 4ohm output for speakers. ...
41 views

### Automotive filter against voltage spikes

I am building a electric vehicle relay controller. Which controls the High voltage relays among other things. I have built an automotive power supply circuit with strong inspiration from this article: ...
37 views

### Automotive Sensor Output

Why does the automotive industry sticks with 5V sensor outputs instead of something like 4-20 mA? Wouldn't it be a solution less prone noise? What are the advantages in using a 5V output instead of a ...
56 views

### Is using a wire rated the same as its circuit's fuse OK?

I want to add a kill switch on the fuel pump relay in my car, which includes extending a line connected to a 15A fuse. I bought some 15A auto wire, but on reflection I'm not 100% sure if that's right. ...
51 views

### Car amp burned out component [closed]

I need help identifying this component on the board of my car amp that has burned out. Electronic circuit board knowledge is pretty much zero for me. But Iām good at fixing stuff so I want to try to ...
91 views

### Confusion regarding jump starting a car

I tried to understand what is going on when one jump starts a car with a dead battery and reading through a lot of explanations, one question remained: You start by connecting the the + poles with the ...
68 views

### Using car radio output jacks for input

On the backside of my Sondpex RUSX903 car radio I found two RCA jacks: a red and a white one. With an adapter cable I connected these to my cellphone headphone jack. So far so good, I noticed two odd ...
100 views

### Electric noise issues in classic car

I tried hooking up a Raspberry Pi (+Hifiberry needs 12 V to 18V input voltage) to my classic car (to be used as music player, radio, BT speaker, no screen, only 2 rotary encoders to navigate through ...
34 views

### Car flasher circuit and grounding

My car flasher circuit can be simplified like so : The factory flasher unit is a standard 2 pin that plugs in series with the switch and the load (indicator lights). I'm attempting to make my own ...
57 views

### Can a 12V (automotive) relay carry more than 12v?

Everywhere I dig around the web (in forums etc.) I see people not recommending more than 12v to go on an automotive relay. Let's look at this one for example: I understand they have been designed for ...
76 views

### Old lead-acid battery inrush charging current

Can an old lead-acid battery have an usually high inrush charging current, such that the alternator belt squeals for the first 30-90 seconds after the engine is started? It is worse in hot weather. ...
67 views

### Will adding a DC-DC converter affect how a modern car operates?

I'm thinking of adding a wireless charger to my car, and adding a Buck Converter to step down the 12V source to 5V for efficiency sake. However, I am worried about the emissions from the DC-DC ...
29 views

### ISO 9141, LIN Bus, K-Line compatibility

I'm designing an automotive scan tool. For now, I'm studying about ISO 9141 and LIN Bus physical layer compatibility. I have a legacy hardware that uses L9637 to perform ISO 9141, through K-Line, but ...
111 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 ...
47 views

### Automotive reverse current and transient protection

Adding reverse polarity and reverse current protection to an automotive circuit seems a bit challenging, especially when driving loads in the 10A range (e.g. seat heater). Diodes on the power line ...
64 views

### CAN Bus Dominant and Recessive?

Why does CAN Bus represents signals with an inverted logic, high voltage for a logic 0 and low voltage for a logic 1? Is there any advantage in doing so?
102 views

### Is there a safe way to operate any type of a tesla coil on a functioning modern car (moving road vehicle)?

(Updated with clarifications) Could a tesla coil be safely built, installed and operated on an active road vehicle which is driving a regular city street? Let's say we want the discharges to be 20-...
23 views

### Automotive Load-dumps, ISO standards & Meaning behind datasheet

Im looking towards using an system basis IC for one of my designs (UJA1164A) and i noticed that under the features & benefits it notes that "Battery and CAN bus pins protected against ...
69 views

### Short to battery & short to ground

In automobile industry, while some of the sensor & valves were connected with electronic control unit, short to battery & short to ground test conditions are taken care against the loads. ...
61 views

### Can anyone help with designing a MOSFET load switch

Can anyone help me design a load switch using the Infeneon IPP120P04P4L p channel MOSFET and the necessary filter components? I would like to use the Texas Instruments ULN2803A darlington driver to ...
72 views

### Surge protector for car USB port

OK so the car manual says not to stick items into the car's USB port while starting the car. Like any good engineer(ing student) I tried to see what will happen if I did so, and am now the proud owner ...
38 views

### Compatibility and Interoperability Between CAN Standards

I'm intended to design a CAN system for a automotive scan tool. So, I need to comprise the main CAN standars used nowadays. Searching on the web I found the following options: ISO 11519-2:1994 ā Low-...
33 views

### How does electric vehicle motors control, torque and speeds beyond base speed?

I'm currently trying to design a electric vehicle motor controller for a Permanent Magnet Synchronous Motor and simulate it using MATLAB. I have considered using the Field Oriented Control (FOC) ...
51 views

### Circuit design for bluetooth ESP32 in my truck

I've been working on this circuit for a few months now with lots of research. Looking for the gurus on here to analyze this board and give me some suggestions/corrections moving forward on parts/...
74 views

### Several positive wires, one negative?

I'll be fixing a motorcycle soon, trying to know if it's possible to have two or more positive wires (connected directly to the battery terminal) but only one negative. There is a usb converter AND ...
146 views

### Need a circuit to detect if something has gone from off-on or on-off

I'm new to circuit design but I'm trying to design a circuit for a power antenna that will send a 5 second pulse whenever it detects a a wire has gone from off-on or on-off. So far I have designed ...
23 views

### Combo Indicator LED / Fuel Pump Relay Kill Switch

I'm looking to wire up simple on/on DPDT switch in my car so that in one position, power is cut to the fuel pump relay and power is sent to a fake alarm LED, and in the other position the fuel relay ...
63 views

### Steering wheel controls with zener diode?

I am looking at my steering wheel schematics and trying to find what are these zener diode doing there? I want to be sure there's no problem feeding 5V from an Arduino to check the ADC values without ...
30 views

### Summing Audio Channels

Iām trying to sum my car stereo output. Factory output has bass on one output and mid and tweeter on another output giving me 2 channels for left and 2 channels for right. Ideally Iād like to sum ...