How to display 0-14.5volts on a 5v display

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1

Hi guys.
I have a display dash in a car with a signal input which is only rated at 5 volts and I want it to display the cars battery voltage reading from the alternator of the car onto this display.
This reading can range from 0 volts when the car is off to 14.5 volts when the car is running and the battery is charging.

So I am assuming i need to get the 12v+ and ground convert them to 0-5V and give the results in a signal.

The inputs i have on my unit are
1/shield
2/ground
3/signal
4/+5V out
5/+12V out

How do i do that?
Are any of these what i need?

https://www.dfrobot.com/product-90.html?gclid=CjwKCAiAqaTjBRAdEiwAOdx9xi-PBy5yFSCEKOuu2P-IDN1i8XqVeqBVbnrO9ua8Hk3ZX5Uj8EdszRoC0y4QAvD_BwE

The inputs i have on my unit are
1/shield
2/ground
3/signal
4/+5V out
5/+12V out

Thanks in advance

2

Hi Gary,

What type of signal does your display require? A voltage divider will give you a relative voltage of 0-2.5V, but its not clear if that will be usable by your display. If it is looking for a digital signal this will not work, if its looking for an analog signal it will be VERY specific voltages so we need to know exactly what its looking for to get an accurate reading.

3

Hi Stephen
Thanks for the reply and please excuse my lack of knowledge on this.
The display is not intelligent and simply displays what ever it is inputted.
If more than 5v is input it will damage the unit as it uses a 0-5V input sensor

However the data imputed can be slightly manipulated via a specific program for the display.

In saying this I assume if we used your part Analog Voltage Divider SKU: DFR0051
Ofourse connecting 12V+ from the alternator & earth then using only the signal out of he dfr0051 to my display unit and adjusting my display unit to convert the raw data by multiplying it x3
eg raw data
minimum value A=0 becomes 0V
maximum value B=5 becomes 14.5V
when the DFR0051 is ouputing
0 will always be 0 volts
5 volts output will show 14.5 volts on my display and all in between 0-5volts will be multiplied by 3 and be shown on my display accordingly.

Am I on the right track? will this work or are there other things I must consider?
Thanks in advance

4

Hi Gary,

Sorry man, I can’t give advice about this without knowing the specifics of the display you are using.

5

ok i understand
well please can you answer regarding


If i input +14.5V into this what will the direct output in voltage be from pin 1S, if i simply place a multi meter onto pin 1S?
Is it +2.9V

Will Pin 1S ever output more than +5V?

Do you have a unit that will reduce the voltage x 3?

Thanks

6

Pin 1S will not go above 5V unless the input voltage goes above 25V.

Yes at 14.5V the output would be 2.9V.

If you would like you could build your own divider using two resistors, this calculator will tell you what values to use http://www.ti.com/download/kbase/volt/volt_div3.htm. I’d sugest using the kOhm(1000) range

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7

Gary,

I think you should use something already set up for Automotive voltages.
E.g. (I’ve seen many cheaper options, this was the first thing listed):

otherwise interpreting the scaled voltage could be very confusing.

Dave

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