HappyFather
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| posted on 25/10/14 at 01:28 AM |
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How do single-wire senders work?
Dear all,
One of the reasons I decided to build the kit was to learn mechanics and how things work. Electrics has been the biggest witchcraft of all. I was used
only to home electrics, which are easy, and the car ones... I built the car with a loom I bought.
I would like to ask if someone is patient enough to explain me how single-wire senders work. For instance, I have a water-temp sensor. There is only
one wire that connects to it. Then I linked the body of the sender to the chassis, for earth. How does that work, how does the reading reach my
Digidash?
Thank you very much for any explanation! Kind regards,
HappyFather
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wylliezx9r
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| posted on 25/10/14 at 04:07 AM |
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I was trying to explain it but gave up so here's an extract from Wikipedia. You have already answered the question yourself sort of, there
isn't a single connection, the body of the sensor is acting as a neutral/earth :
Types of sensor
As the sensor's temperature changes, its resistance changes accordingly. Depending on the type of sensor, the resistance will either increase or
decrease.
In negative temperature coefficient (NTC) sensors, the internal resistance will decrease as the temperature rises (and vice versa).
In a positive temperature coefficient (PTC) sensor, the opposite is true. Its resistance will increase with rising temperature.
Most automotive coolant temperature sensors are NTC sensors.
Operation
The ECU sends out a regulated reference voltage (typically 9 volts) to the coolant temperature sensor. The voltage drop across the sensor will change
according to the temperature because its resistance changes. The ECU is then able to calculate the temperature of the engine, and then (with inputs
from other engine sensors) uses lookup tables to carry out adjustments to the engine actuators, i.e. change the fuel injection or ignition timing.
This is necessary because in order to run smoothly, a cold engine requires different timing and fuel mixture than an engine at operating
temperature.
[Edited on 25/10/14 by wylliezx9r]
I spent a lot of money on booze, birds and fast cars. The rest I just squandered.
George Best
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snowy2
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| posted on 25/10/14 at 06:29 AM |
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the vehicle chassis is the second wire......never forget thet the whole car is one part of the circuit.
Take a look at an article i wrote a few years ago and is posted to here on the subject of wiring your car,
Wiring your car
sometimes you are the pigeon, most of the time the statue.
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snowy2
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| posted on 25/10/14 at 06:42 AM |
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but your question......mostly the sensors are resistors which vary with temperature as the vehicle warms up the resistance changes and the sensor
will allow more or less current to flow depending on temp. this is then read on the guage.
sometimes you are the pigeon, most of the time the statue.
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HappyFather
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| posted on 29/10/14 at 12:31 AM |
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Thank you very much all for the replies!
And a special thank you to Snowy2 for that document because it probably will answer other questions I'll have in the future when I start
mod'ing (namely to get a cig lighter in to charge the phone/GPS).
After reading Snowy2's document and see using chock blocks for the dash I though of all the hours I spend crimping spade males and females on
the loom and digidash cables... Why didn't I think of that?!? It would have saved me many hours...
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snowy2
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| posted on 29/10/14 at 08:03 AM |
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I have taken some heat over recommending using chock blocks however in all the years I have been wiring kit cars (since 1988) they tend to be more
reliable connectors.
[Edited on 29/10/14 by snowy2]
sometimes you are the pigeon, most of the time the statue.
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MikeRJ
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| posted on 29/10/14 at 08:31 AM |
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quote:
Originally posted by snowy2
I have taken some heat over recommending using chock blocks
#
Not surprising, they are the devils own work. If you see choc blocks in car wiring then I know to expect the worst.
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Non custom
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| posted on 29/10/14 at 09:17 AM |
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I agree ^^ what's wrong with a good ok soldering iron and some heat shrink , and proper joints when needed (spade clips still a bodge IMHO ))
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snowy2
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| posted on 29/10/14 at 07:21 PM |
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Ah yes but if you actually read the article you will see that I sugest other methods how ever I have never had a chock block connection described
above fail. Where as no end of bullet and spade connectors have failed.
Since I am actually a qualified car electrician and speak from experience you can decide what you like about advise ofered. But chock blocks are
better than many methods and harder to do incorrectly.
When I look at some cars at the shows its obvious that 99% of the effort went in the bling And 1% on the electrics.
There is also an immense amount of nutsack in the kit car world often spouted by car assemblers as opposed to car builders. My advice is for those
who want to build their car. Your at liberty to improve on any connector you like but the offerd advice is sound and works reliably.
sometimes you are the pigeon, most of the time the statue.
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