For ages i've been looking at a set of gauges and not buying them cause they don't have a fuel gauge. then i had this idea ........
Fuel gauge sender is based on resistance, has anyone got a simple wiring diagram on how i can get 10 leds to light up at different resistances (and
set each light to a fixed value).
Thinking of making a line of LED's to go under my bright 6 to indicate fuel level.
i will have a look at work, see what i can knock up, do you know the resistances of your fuel gauge sender(or a standard one) at full and empty?.
Ray
Hi MikeR,
Sounds like you want a LM3916 LINK
should do what you want with minimum fuss, free smaples as well
thats what i was thinking, would also possibly give the option of having LED flashing when fuel is low/near empty.
we use these at work, so will have a play, may even be able to knock up some PCB's
Ray
seem to remember you can buy flashing LED's thought i'd just get the last one as a flasher.
As for resistance - not off the top of my head. Planning on using two gauges so depending on price it would be two gauges or adjustable.
The first is a standard ford one, the second a standard MGF one for when i go fuel injected. Seem to remember the MGF one was something like 5 to 105
ohms (can't remember which was full / empty tho)
Please be very very careful here... You are designing an electrical device that is NOT SEALED, and are dropping it into a tank full of Petrol or worse
still a nearly empty tank of fumes and some petrol.
What ever you do... just make sure you do it right.
Worst case you could do a good imitation of a Terrorist Attack without a Target
I have seen quite a few inexperienced postings in the Electrical section, and a few equally ill-informed replies.
Electrics on a car is an area where a lot of people do not properly understand the subject or the effects of getting it wrong.
A Car fire is one thing,, but Starting it in the Fuel Tank is another.
You are taking an unusual step of designing a fuel gauge.. no problem there... but the consequences of getting it wrong are Life threatening, are
worse. ie a Major Burns to your soft tissues.
Just make sure you get it 110% right.
I dont want to read about you being in a hospital burns unit with half your skin missing, and your hands tied up in those Roasta bag things.
Signed:
Scared of Cambridge (Scared for you)
Monkeyhunter..
That is the funniest avatar I have seen, especially when is eyeball is flailing around before it snaps off the cord..........fantastic
Where'd you get it?
Paul
wilkingj, i think you've misunderstood, we are not designing a fuel sender unit, only the gauge(which will be sat in the dash well away from any
source of fuel)
the piece sat in the tank, will be a standard fuel sander, be it from donor car or new.
Ray
yep - totally correct, this is the fuel gauge that connects to the signal the standard car sender is giving us.
As a side point, my mate who does Fuel Injection systems for a living (BMW / Toyota / ROVER etc) still thinks i'm going to burn with a standard
locost as we don't go through 10% of the hoops he has to.
I have a piece of translucent green tube connecting between two outlets on the tank, one top, one bottom. Seems to work ok
quote:
Originally posted by skydivepaul
Monkeyhunter..
That is the funniest avatar I have seen, especially when is eyeball is flailing around before it snaps off the cord..........fantastic
Where'd you get it?
Paul
You only want the last LED to flash if it's the only one lit. It will get annoying otherwise. Use a minature adjustable pot on your PCB to trim the "full" level light on your display. Easier than using fixed resistors.
You'll like happy tree friends and
joe cartoon then. Itchy and Scratchy for real people.
National want 10 dollars for the free sample . Anybody else find this contradictory?
[Edited on 27/9/05 by Peteff]
National want 10 dollars for the free sample of the little bit of electronics. I've got no issue with paying the money but can smoeone confirm,
does the chip take volts or resistance as its trigger signal & how do i adjust the signal to fit into my range?
(i last did electronics as a 1/3rd of a GCSE 17 years ago)
had a quick look at it last night, an LM3914 would be better suited, as it has hysterisis functions(will stop the lights going up and down as the fuel
sloshes about in the tank), you will also need a voltage reulator(LM317 or the like) to make sure theres no fulctuation in supply voltage, the LM3914
can work from a 0 to 5v input, so it sjust a case of some fiddling with resistors to adapt the output from your sender.
Ray
[Edited on 27/9/05 by rayward]
quote:
Originally posted by rayward
wilkingj, i think you've misunderstood, we are not designing a fuel sender unit, only the gauge(which will be sat in the dash well away from any source of fuel)
the piece sat in the tank, will be a standard fuel sander, be it from donor car or new.
Ray
Point made very loud and clearly now ........ thanks
What ever is designed will be pushed past my mate (who i've probably bored everyone to death saying designs fuel tanks / pumps / lines for a
living)
As you seem to know something about this, how do third party gauge manufactures get away with this? They can't know what level sender is going to
be used.
The key to safety is NOT passing a big current through the fuel sensor, ie. make the guage high impedance.
There is some information here:
http://www.westol.com/~beaurega/gas.htm
Under "How the simple circuit works."
Be careful !
As for LED dash displays I really like the one on 'Bob C's locost which does fuel on a bargraph amongst everything else:
http://freespace.virgin.net/bob.carter/locost_build.htm
quote:
Originally posted by iank
The key to safety is NOT passing a big current through the fuel sensor, ie. make the guage high impedance.
quote:
Originally posted by MikeR
Point made very loud and clearly now ........ thanks
How do third party gauge manufactures get away with this? They can't know what level sender is going to be used.
OK,
just a bit of background info,
I am a time served electrical technician, have ONC's in electrical and electronic engineering,and an HNC in electronics.
from the info on sender units i have found , the current at the sender would be approx 50mA at 12volts.
the circuit i have designed(all but calibration to appropriate sender) will run 5volts at a MAX of 30mA through the sender unit.
however, from the comments posted here, i do think that it would be best not to bother making this info available, then i can't be blaimed for
anything that may or may not happen if the people building and/or using this circuit don't fully understand the principles involved.
Ray
quote:
Originally posted by rayward
the circuit i have designed(all but calibration to appropriate sender) will run 5volts at a MAX of 30mA through the sender unit.
Ray
quote:
Originally posted by rayward
however, from the comments posted here, i do think that it would be best not to bother making this info available, then i can't be blaimed for anything that may or may not happen if the people building and/or using this circuit don't fully understand the principles involved.
Ray