How to power a dash cam without a car adapter?

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ChrisFromCali

Joined Jan 4, 2024
1
Purely out of curiosity, I was trying to power an old dash cam of mine with a 5V supply. The car adapter it came with has an output rating of 5V 1.5A. I have a 5V source in series with a 2.2 ohm resistor (Maths says it should be 3.3 ohms to get 1.5A but it measured a bit low so I went with a 2.2 ohm resistor and measured 1.51A). I put the dash cam in series with this but it does not turn on. What am I doing wrong? Also please don't hate me for the exposed wires.
 

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eetech00

Joined Jun 8, 2013
3,942
Purely out of curiosity, I was trying to power an old dash cam of mine with a 5V supply. The car adapter it came with has an output rating of 5V 1.5A. I have a 5V source in series with a 2.2 ohm resistor (Maths says it should be 3.3 ohms to get 1.5A but it measured a bit low so I went with a 2.2 ohm resistor and measured 1.51A). I put the dash cam in series with this but it does not turn on. What am I doing wrong? Also please don't hate me for the exposed wires.
You don't have to worry about the current from the adapter as long as it is rated higher than the camera requires.
The camera will only draw from the adapter what it needs to operate.

If you put a resistor in series with the adapter, you are reducing the amount of current it can supply. Don't do that.
 

Jon Chandler

Joined Jun 12, 2008
1,048
If you put a resistor in series with the adapter, you are reducing the amount of current it can supply. Don't do that.
Actually you're causing an I×R voltage drop. Remove the resistor.

Some chargers may require a resistor or short bridging the DATA PINS to provide more than 500mA but that's a different matter.
 

dl324

Joined Mar 30, 2015
16,911
Welcome to AAC!
What am I doing wrong?
You don't understand fundamental principles.
  1. A 5V device will only use the current that it needs.
  2. Adapters are specified to provide more than the maximum current that the device will need.
  3. Dropping resistors, voltage dividers, and series diodes are almost never a good way to drop voltage.
I put the dash cam in series with this but it does not turn on.
Your pictures don't show how things are connected. The adapter output should be "across" the device:
1704383803376.png
 

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