Do you have a question? Post it now! No Registration Necessary
Subject
- Posted on
ohm converter
- 06-07-2005
June 7, 2005, 4:14 am

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

Re: ohm converter
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:


Re: ohm converter
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:


Re: ohm converter
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

--
++++++++++++++++++++++++++++++++++++++++++
Jenal Communications
++++++++++++++++++++++++++++++++++++++++++
Jenal Communications
We've slightly trimmed the long signature. Click to see the full one.

Re: ohm converter
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
Site Timeline
- » anybody want this stuff?
- — Next thread in » Electronics Down Under
-
- » laserjet II or III parts free
- — Previous thread in » Electronics Down Under
-
- » Aussies Love EVs ?
- — Newest thread in » Electronics Down Under
-
- » Replacing NiCd batteries in an obsolete Uniden UH-052XR radio?
- — Last Updated thread in » Electronics Down Under
-
- » riflettometro cercasi
- — The site's Newest Thread. Posted in » Electronics Hobby (Italian)
-