ohm converter


ok ive got a fj40 landcruiser thats now on straight lpg they want 200bux for
the converter to use the standard gauge with the lpg tank so i said stuff
that
anyway the lpg sender is 0 ohm empty and 90 ohm full and the standard gauge
is 120ohm empty and 17 ohm full
so what im wanting is a simple circuit so i can hook them up and have a
proper gauge
i can build circuit boards and stuff im just no good ad designing circuits i
just dont know where to start
Reply to
pcman
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I can't think of a passive design that will do this (off the top of my head). there could be one ??
an easy way of doing it is using an inverting amplifer design. but you would have to work with voltage/current references not resistances. that's easy to do, but you need to find out a little bit more about the electrical characteristics of the fuel meter.
here is one way i would do it (basic overview)--
- i would supply the tank a constant current, say with a current mirror (you can configure an LM317 as a constant current source). that would give you a resistance to voltage conversion.
- feed this voltage into an inverting opamp configuration. This will produce an inverted voltage.
- What you do with the output voltage (or current) depends on how the fuel meter guage works. you might find that the meter is measuring current flow for example. if so, then you can configure the opamp to supply a given current.
me personally, if you are not prepared for a few days of analysis, building, testing etc.. then i would just pay the 200 moola. alot of time and energy goes into designing something that reliable and ruggled. $200 sounds like a cheaper opinion.
i would try to build it though, it is sounds like a fun project ;)
cheers
pcman wrote:
Reply to
fred.kroft
Maybe I am dreaming but the solution seems simple to me - just install a switch that changes the input to the fuel gauge from the petrol sender to the lpg sender, BUT include a 18 ohm (or so) resister in the lead from the lpg sender.
Note that the full to empty range of both senders is fairly close, but that the lpg sender empty is 0 whereas the petrol empty is 17ohms. So if you just compensate for this initial resistance you should have a near enough gauge for your lpg. Remembering that fuel gauges only provide a rough idea of fuel capacity, this should be near enough and certainly better than spending $200 for ???
David
snipped-for-privacy@gmail.com wrote:
Reply to
quietguy
And put 360Ohms across the meter to bring the full-scale resistance correct. You could be pedantic and put it across the series resistor as well, but it's close enough either way.
Ken
"quietguy" wrote in message news: snipped-for-privacy@REMOVE-TO-REPLYconfidential-counselling.com...
Reply to
Ken Taylor
And don't forget a new scale on the guage as the sender operation is now reversed (ie fuel giage says full when it is actually empty!)
Alan
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Reply to
Alan
Yes, David did mention that. Mind you, it'd be a conversation piece - "Hey look, my fuel economy is so good I generate fuel when driving!". :-)
Cheers.
Ken
Reply to
Ken Taylor
Just put a sticker on the guage to read empty as full and full as empty .
European like the blinkers / wiper washer
in
a
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have
Reply to
FruitLoop
i musnt have been thinking straight when i typed the message i took my dash apart and repainted the gauge so it looks correct then put a 18 ohm resistor inline ite better than having no gauge and seems pretty acurate sofar
thanks for the help guys i might put a 360ohm in aswell see if that makes it better
correct.
lpg
just
gauge
fuel
a
Reply to
pcman
Excellent! Funny how the simplest solution often eludes us (thanks David!). Thanks for the feedback.
Cheers.
Ken
a
it
in
a
spending
standard
have
Reply to
Ken Taylor
feedback is always good ive added the info to our 4x4club so all the guys that run lpg can use this tip on theres
im happy having a fuel gauge, when you cant get a jerrycan of petrol its a really good thing
David!).
put
makes
but
wrote
install
the
lpg
but
said
Reply to
pcman

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