Wireless temperature gauge

Thread Starter

teliocide

Joined Sep 26, 2013
71
I need to add an extra engine temperature gauge and am trying to avoid running wires through the firewall
I would prefer not to use microprocessors or computers to this.
Any suggestions on how to proceed?
Thanks
Greg

Trans-temp.jpg
 

DickCappels

Joined Aug 21, 2008
6,317
Condition your temperature signal and apply it to a voltage-to-frequency converter -transmit the frequency generated as a string of pulses via your transmitter National/TI's LM331 comes to mind as an easy way to do it. An on/off keying system would work. To decode the stream, feed the frequency into a frequency-to-voltage converter like the LM2917 . The temperature may be read out with a digital panel meter(example).

You can use any kind of modulation for which you can find a suitable transmitter - receiver pair or pair of transceivers. It is a good idea to not add an antenna to the transmitter so you have less chance to cause interference with other devices on the same frequency. You should probably limit the duty cycle so as to not jam the channel. Toward that end you could use a second transmitter-receiver pair to request the sensor end of the system send the temperature for some period of time.
xmit-rcv edample 1 xmit-rcv example2



For your entertainment:
https://www.youtube.com/watch?v=XLwYKUFnNAg
 

Thread Starter

teliocide

Joined Sep 26, 2013
71
Greetings Dick
Thank you very much for your detailed reply>
I follow what you are describing but to design this (create a feasible functioning package) is out of my league>
But thanks again I am know well armed to burden competent and capable friends
 

wayneh

Joined Sep 9, 2010
16,384
Greetings Dick
Thank you very much for your detailed reply>
I follow what you are describing but to design this (create a feasible functioning package) is out of my league>
But thanks again I am know well armed to burden competent and capable friends
If you can’t build it, buy it. I have one of these and it’s impressive.
https://tempstick.com/
It would require hacking to work the way you want, like adding wires to move the sensor, but all that would be easier than building from scratch.

There are probably less expensive options that might even be better for your application. You’re certainly not the first person to want remote temperature sensing. No need to reinvent the wheel.
 

Thread Starter

teliocide

Joined Sep 26, 2013
71
Unfortunately Wayneh there are a lot of square wheels around so building oneself a nice round one is good>
I can assemble electronic stuff with a very good success rate - I have not been trained in the design of circuits>
I can work out the bits I require but I lack the knowledge to be able to link the bits together.
Cant be awesome at everything :))
 

Janis59

Joined Aug 21, 2017
1,169
Somehow feel the Arduino here may be simpler and sure more stable (the engine itselgf is violent EM spike producer). Digital i2c interfaced sensor of G-NIMO-003 alias TSYS-02D (VSOP) thermometer (1 USD) then arduino for reading that info (0,95 USD) and sending to Nordic-24L or Noerdic24L+ tablet (2,4 GHz, 1,05 USD), then One more arduino for receiving the data from Nordic and reconfiguring it like the figures. Last is choice - normal display with normal digital interface (as white man do) or four to five digit LED voltage display (D.Cappells shown one but ebay sells even 10-20x cheaper as well, labeled as three wire LED voltmeter) via the arduino pwm output, but 8 bits are the best ever accuracy. The problem there is that good display costs a good money (25 USD or liguid-ink fascionate even 40-60 USD). As the arduino is rather well covered with ready-made libraries, the programming skills may be set on rather low level, but not nil. And my softwearist just in last week found a shocking fault in Nordic Arduino library making the job impossible. Thus he wrote own what now is functioning properly.
 

Thread Starter

teliocide

Joined Sep 26, 2013
71
Thanks Janis59
I am well aware of the multitude of Arduino solutions to this. There are millions on line.
I rather like DickCapples approach that is:
Analog sensor >>AD converter >>modulated RF>>DA converter>>Analog display
If you can assist it would be great
 

wayneh

Joined Sep 9, 2010
16,384
Analog sensor >>AD converter >>modulated RF>>DA converter>>Analog display
If you can assist it would be great
A very common sensor is the LM35. It produces a voltage proportional to temperature. But it’s the same shape, size and package as a little black transistor. (Just look it up, you’ll see what I mean,). It would need a thermowell to sit in to be protected against...everything. Like a hollow, stainless steel finger.

On the opposite end of your scheme, you could use a cheap voltmeter. There are tons of them out there of all different sizes, colors, etc.

All the stuff in between is out of my wheelhouse. I understand the idea but I’d have to do a lot of work to make it all work together. That’s why I’d lean towards buy versus make for this. I’d want to at least know what the commercial choices were, and how they work.
 

DickCappels

Joined Aug 21, 2008
6,317
The hard part seems to be the communications link since some kind of information encoding and decoding would be needed. When I added a thermostat to my car to supplement the "Engine Hot" light I found where the wires that ran between the passenger compartment and the engine compartment and slipped my own pair of wires through the passage. Have you looked for such an opportunity in the firewall through which you want to send the signal?
 

Janis59

Joined Aug 21, 2017
1,169
RE: Teliocide
Then use a VCO which whistles as larger voltage as larger frequency. And let it modulate the RF part. In receiver just provide a simplest RC frequency measurer giving data as voltage to the LCD panel. But it isnt much simpler but is sure less acurate than Atmel-328 version. For transmitter part, just common base by RF and CE by DC capacitative divider oscillator (better if with PI filter in output) is just like what You want http://ebook.pldworld.com/[mirroring]/www.sentex.ca/~mec1995/circ/archive/rfosc-1.htm
 
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Janis59

Joined Aug 21, 2017
1,169
However I bit meditated about the chauffer sitting whole the day after day in the cabin where 30 cm distance the 50 mW transmitter is radiating all the time. And digital version where once a second a nanosecond short handshaking happens between 5 mW strong subsystems. I would like to slepp over the second and run away as soon as possible from he first.
 

Thread Starter

teliocide

Joined Sep 26, 2013
71
I have looked at modifying those domestic units but my primary concern is the very slow refresh/update rate they have>
Commonly around 2 mins.
 

DickCappels

Joined Aug 21, 2008
6,317
I have had a few of those inexpensive thermometers. The ones I had were slow because the external thermistors were mounted in a plastic capsule which would change temperature in air very slowly.

A shortcoming those air termperature thermometers is that they have limited temperature ranges. I really don't think they can go all the up to typical engine coolant temperatures.
 

Thread Starter

teliocide

Joined Sep 26, 2013
71
The external thermistors are mounted in a plastic capsule to avoid short term temperature changes
My past experience in Microbiology laboratories where we used incubators, sensors were placed in a jar of silica gel>
Effectively we were integrating temperature over time as the long term average temperature is what we aimed to control.
This is the sensor for temperature monitoring NOT the sensor from the thermostat.
 

danadak

Joined Mar 10, 2018
4,057
Have you looked at ESP8266 or ESP32 solutions ?

Google this "esp8266 remote temperature sensor", lots of projects.


Regards, Dana.
 

Thread Starter

teliocide

Joined Sep 26, 2013
71
Thanks Dana
Very neat and relatively simple but still seems an overkill solution for what I would like
I am still hoping a simple solution eg
Analog signal >>>>> Voltage to frequency conversion >>>>>> Carrier modulation >>>>transmission >>>> Reception>>>> Demodulation>>>Frequency to voltage conversion >>>>> analog signal

Thanks again
Greg
 
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