I intend to use the arduino to link a temperature sensor to an analog dial like the ones on car dash boards. Has anyone got any ideas on how this can be achieved. many thanks
Tell us more about the temp sensor and dial you intend to use. Post some links?
Paul
Do you mean a genuine analogue dial, or a screen representation of one?
There are at least several ways to do that but before we get into that do you mind if
I ask what sensor you plan to use for temperature ? You didn't mention if the "temp" you were planning
to measure was engine temp or ambient temp.
You have two choices for the analog meter. You can just buy a meter that measures voltage and use a PWM
output with an RC low-pass filter convert the pulses to filtered dc and use that to drive your meter but
you might have trouble finding a meter with a full scale reading of 5Vdc. The other way is to use an ammeter
with a series resistor. This gives you more flexibility because you can choose a resistor to convert the current
to the full scale value of your meter , following the guidelines based on Ohm's Law.
Ohm's Law: E(voltage)= I (current) x R (resistance) |Where E is in Volts, I is in Amps and R is in ohms.
Given a circuit with a maximum voltage of 5V dc.
and an ammeter with a FS (Full Scale) rating of 1 mA (0.001 A) , and an R(m) (internal resistance) of 81 ohms,
E=I X R => R = E/I = 5V/0.001= 5000 ohms.
What this tells us is that if we want our current to be 1 mA at Full Scale, the TOTAL resistance in our circuit
must be 5000 ohms (5k ohms). But our meter's internal resistance is 81 ohms so we are missing 4,919 ohms.
Where can we find this ? Realistically , it would not be easy. It is possible to order custom 1% resistors (or better)
but it a lot easier to use a 4.7k ohm resistor and a 500 ohm potentiometer. Set the pot for 300-81=219 ohms
and put it in series with the 4.7 k ohm resistor and the 81 ohm milliammeter and then calibrate it for your
maximum output of your PWM pin after adding a 4.7 k ohm RC filter resistor with a 0.1 uF cap to 1 uF cap.
to smooth out the PWM so it is filtered dc. It is unlikely you would get 5.000 volts out of a PWM pin so you
need to command full scale output from you pin and adjust the pot for full scale on the meter. Now you have
a way to drive the meter which is in no way connected to your temperature sensor. Once you choose your
sensor and connect it and collect your sensor data then you can tell the meter to display it accordingly.
That's one way. I'm not saying it is the best, but you asked how it could be accomplished and that is my
answer.
You really don't have to worry about filtering the pulsating DC before you feed it to the meter. The inertia of the meter will do all the filtering for you.
Don
That's right ! I completely forgot about that. Good point Don .
Posting the same question in two boards doesn't help anyone. All it does is dilute the effort and piss everyone off.
Do you have a link to the details of that dashboard? Hard to offer any advice without knowing what it is and how to interface to it.
That out of a loader?
Your going to have to dig deeper and identify the actuator .With that you will have to determine its pin out , then determine its language or how the ECM talks to it .
Unless you have an original factory schematic and parts list of the cluster , your going to have to take it apart. .
The reason i put it in multiple places is because i didnt near where it would best fit.
Chris1448:
That out of a loader?Your going to have to dig deeper and identify the actuator .With that you will have to determine its pin out , then determine its language or how the ECM talks to it .
Unless you have an original factory schematic and parts list of the cluster , your going to have to take it apart. .
yes it is out of a loader. i have the original data sheets that identify a signal pin for this and under signal it just says 'ohm' any idea what that means chris
the gauge i intend to use is a pre built jcb dash panel with the gauge pre mounted, i have attached a picture, also the temp sensor is a LM 35 sensor
It would have been nice to mention that in your original post.
You still have not said anything about engine temp. If that's what you want to measure please say so.
Is there any information on the meter ?
What else do you need ?
Do you need help setting up the sensor ?
Where's the datasheet ?
Have you looked at the datasheet ?
Your going to have to dig deeper and identify the actuator .With that you will have to determine its pin out , then determine its language or how the ECM talks to it .
There's three guages.
Do you want to use the "temp" guage for temp ? (you never know)
If so why the talk about actuators ? I thought that was only for the speedometer, which is mechanical not electrical.
Can you find out the internal resistance of the temp guage in the panel ?
okay, i have the data sheet and that tells me that there is a control pin and the word ohm, probably suggesting that it is done by resistance if i am correct? i need help to find out wether i want to achieve is possible and if so how would i go about it, if you need any more information to help please say and i will do my best to find it and get it to you
datasheet for what ?
Can you answer the questions in my last post please ?
Post the datasheet so everyone is on the same page.
Post the datasheet so everyone is on the same page.
Until he does that or at least gives some more information all he will get is guesses. Any of the three gauges could be electrical, mechanical, hydraulic, etc. If electrical they could be moving coil, stepper motor, servo motor, etc.
Don
Not familiar with a "Hauler" but I remember people used use an electric drill to run their speedos back
so I know that's mechanical. The other two , your "guess" is as good as mine.
yes i want to use the temp gauge for temp. i didnt mention actuators that was someone else. here is a picture of the part of the data sheet that talks about the temp gauge
how do i find the internal resistance?
i have put a pmw signal from the arduino through the signal pin for the gauge and i am getting movement. This ranges from anologWrite 0 to analog 60. i have worked out these resistances and they range from 24.25 ohm to 55.50 ohm if that helps?
sorry i cant post the data sheet as i only have it on paper
thank you
It looks like pin 9 is Vcc and pin 16 is ground and pin 13 is the meter input. It sounds like you already
have the polarity correct. How many electrical connections on the meter ?
The datasheet says the resistance is 130 ohm at 90 deg C and 2 ohm at 140 deg C.
This must be from the sensor.
That's a range of 128 ohm deviation for 50 deg C deviation of temp.
The LM35 generates 10mV /per deg C so that's 1V at 100 deg C.
Analog input is 0 - 1023 . 1023/5=204/V input. Sensor should read value of 204 at (1 That's not a temperature guage, that's a speedometer , and it's mechanical not electrical.(1V) at 100 deg C.
Sensor output should be 1V at 100 deg C.
The PWM is 8 bits 0 - 255, with max volt at 254 which is 19.6 mV per bit or roughly 1 V per 50 bits
(Value OUTPUT = 50 => GENERATES 1V , 100 generates 2V , 150 generates 3V etc...)
You need to get the meter to display 100 deg
You need to get the sensor circuit working and put it in boiling water (with the wires insulated with silicone or
epoxy) (100 deg C) and use that as your reference to drive the meter to 100 deg .
How do you have the meter connected electrically ?
Are you using a series resistor like I described previously?
Any labels on the terminals ?
anges from anologWrite 0 to analog 60. i have worked out these resistances and they range from 24.25 ohm to 55.50
Show your math work for the above statement
Are you able to drive the meter full scale ?