# Thread: Has anyone tried Prosport Gauge senders?

1. One of my problems is ... your talking way over my level of understanding. I've been sitting on the software side of things for too long and need a simple set of instructions as to what to do. I can see you're trying to be really helpful but I'm still no wiser.

Best to assume I am still in kindergarten on the hardware front, while on the software side I have a system that can not only read values from the car's CAN bus but also change the setup of the car without touching the normal controls.

2. Ok, your powered sensor puts out 0-5V so that should be okay. (But if you want to decrease the range from 0-5V to 0-4V etc, then the resistive/voltage divider applies.)

Your temp sender is a resistance. You do not measure resistance per se - you measure the voltage across it & current through it.
Instead of measuring the current (and voltage), we add a series resistor and merely measure the voltage across it....

Hence your temp sender needs another resistor placed in series and have a voltage applied....
Call the temp sender R2.
Connect them between a voltage Vin.
You then measure the voltage across the temp sender R2 which is Vout. (See the Wiki voltage divider link as above.)

You need to calculate the R1 value based on (1) our temp sensor range, (2) the supply voltage Vin, & (3) your desired output voltage range Vout.

Be aware that Vin needs to be regulated. Hence you might use another regulated source or the FB's 5V etc.
The problem is that you may want a good voltage range across the temp sender which means a higher voltage supply. This is to make the added resistor as large as possible to reduce the current. (Increased current means more load on the supply (eg, FB) as well as higher resistor wattage ratings.) An alternative is to use a constant current source (typically 2 transistors and a resistor or 2).

For comparison, many vehicle temp gauges are supplied by an 8V regulated supply.

Though the above sounds complex, it's just "one bit at a time". I've given you the full byte (in a long-word).
It is application of one main thing - Ohm's Law (V=IR).
Also a bit of power ratings (P=VI) and understanding basic circuit theory that series voltages add up (to the supply voltage) and the current flowing through a path is equal through each component (which is really Ohms Law V=IR).

It's an iterative design. Set your desired temp range (and hence resistance range) and what voltage that should correspond to for your FB.
You then iterate R1 based in Vin supply voltage and source.....
... and then, more Chinese take-away programming tricks....

3. Here a couple of threads to look at. I was having a hard time understanding voltage dividers also and these were clear enough that even I could understand them.

The third link is an online voltage divider calculator that will help you find the correct resistor size.

How do I...

http://www.mp3car.com/vbulletin/fb-d...-controls.html

http://www.raltron.com/cust/tools/voltage_divider.asp

4. Thanks to both of you.

5. For the temp sensor ...

Using a 400ohm resistor I will get signal voltage in the range 0.37V - 3.491V
Connect the 5V out on the FB to one side of the resistor. Connect the other side of the resistor to one of the sensor wires. Connect the other sensor wire to the FB signal. Connect the FB Ground to ground.

For the pressure sensor...

Connect battery to 12V wire on the sensor
Connect signal wire on sensor to FB signal
Connect the Ground on the sensor to ground
Connect the Ground on the FB to ground

6. Originally Posted by Petrie
For the temp sensor ...

Using a 400ohm resistor I will get signal voltage in the range 0.37V - 3.491V
Connect the 5V out on the FB to one side of the resistor. Connect the other side of the resistor to one of the sensor wires. Connect the other sensor wire to the FB signal. Connect the FB Ground to ground.

For the pressure sensor...

Connect battery to 12V wire on the sensor
Connect signal wire on sensor to FB signal
Connect the Ground on the sensor to ground
Connect the Ground on the FB to ground

close, but connect the "other sensor wire" to ground instead, and the FB signal to the connection between the resistor and sensor.

7. For the temp sensor ...

Using a 400ohm resistor I will get signal voltage in the range 0.37V - 3.491V
Connect the 5V out on the FB to one side of the resistor.
Connect the other side of the resistor to one of the sensor wires and to FB signal.
Connect the other sensor wire to ground.
Connect the FB Ground to ground.

8. FWIW the third FB gound pin doesn't have to be connected to anything.

9. ^ ok, thanks

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