k33ts
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| posted on 12/1/06 at 08:12 PM |
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electronic curcit for fuel gauge
is anyone out there anygood at electronic circutry.
ive been looking at buying new clocks except all the ones i like dont make a fuel gauge.
i was thinking of having a row of leds maybe 8-10 going green to red for fuel instead of a gauge so i can have the gauges i like
could anyone draw me up a circut obviously it will depend on the sender which im geussing would be a case of measuring the impedance from empty to
full
any help would be greatly appreciated.
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MikeR
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| posted on 12/1/06 at 08:46 PM |
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not much help but do a search its been covered before as i wanted to do this. People get scared - fuel, electrics, creating your own circuit putting
different voltages / amps down it, fuel vapour, bang........
love to have a similar thing tho!
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k33ts
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| posted on 12/1/06 at 09:29 PM |
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found it cheers, perhaps ill forget that idea then.
did anyone actually try it in the end then?
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RazMan
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| posted on 12/1/06 at 09:37 PM |
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If they tried and it went bang ........ who will ever know?
Cheers,
Raz
When thinking outside the box doesn't work any more, it's time to build a new box
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k33ts
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| posted on 12/1/06 at 10:05 PM |
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how about 1 light coming on when you get down to say 1/4 tank
i know this sounds like a bodge but would this work and be safe
fixing the proper gauge for the sender under the dash and gluing a micro swith to the face so the needle switches it
go on laugh but i need something as im determined not to have s**tty looking clocks
and if dont have anything ill always b running out siv head
[Edited on 12/1/06 by k33ts]
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Popee
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| posted on 12/1/06 at 10:41 PM |
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Electronics
I knew this Degree in Electronic Engineering Im studying would come in use someday.
The Easiest way would probably to use a LM3914 Bargraph Display Driver
If you could get me a wiring diagram for the type of sender your using and also its resistance when its at the top of the swing and the resistance and
the bottom of the swing I could sort you out with circuit diagrams and whatever chips you need to do it, as well as pointing you in the right
direction to components
Little bit busy at the moment with exams, but should be able to sort it no problems.
Lee
Lee
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k33ts
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| posted on 12/1/06 at 10:54 PM |
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the only reason i came up with this bodge idea is because there has already been a discussion on this forum about the safety aspect. ie messing with
electrical circuts going through the petrol tank.
i appreciate your help but to be honest after reading the discussion im to afraid to try it fryed chicken springs to mind.
it would only take a small mistake to make one hell of an explosion
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MikeR
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| posted on 12/1/06 at 10:55 PM |
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Once you've done the circuit could you pass it to me. As i've said in the other thread, my mate designs fuel systems for a living.
I'll try and persuade him to cast an eye over it - i'm not sure he'll say yes (liabilities etc) but its worth a try.
Might also be worth mentioning how to adjust the circuit so others can use it with different senders.
I'll happily throw a few beer tokens your way if you can sort us out.
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MkIndy7
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| posted on 12/1/06 at 11:31 PM |
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Why are voltages being put anywhere near the tank, surely it can be done or resistance or even continuity.
Something like a cheep moisture detector in the side of the tank or hung down from the top at 1/4, 1/2, 3/4 and full levels whould do the trick.
Thats pretty much how detectors called a "watchman" on a heating oil tank work to show the level to the occupants of the house withought
going outside. As the (oil in this case) makes the circuit it confirms its full to that level.
Only trouble is it would prob read funny in the corners unless you set the detector behind a baffle or in a tube.
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MikeR
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| posted on 12/1/06 at 11:41 PM |
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I last did electronics at GCSE [cough] years ago.
To measure resistance - which is all the fuel sender does you need some current to be passing - ie some volts.
Now in theory this is really easy, its PROBABLY (i've no idea) designed for 12 volts, if we put 3 volts through (or less) and measure resistance
then we should be safer ......... look at it another way, lots of people have been making fuel senders since the 1950's. Can't be that
difficult.
I believe westfield do one - except its not cheap.
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NS Dev
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| posted on 12/1/06 at 11:45 PM |
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quote:
Originally posted by k33ts
how about 1 light coming on when you get down to say 1/4 tank
i know this sounds like a bodge but would this work and be safe
fixing the proper gauge for the sender under the dash and gluing a micro swith to the face so the needle switches it
go on laugh but i need something as im determined not to have s**tty looking clocks
and if dont have anything ill always b running out siv head
[Edited on 12/1/06 by k33ts]
My sentiments too, no crappy clocks in my car either!!
No fuel gauge either though!
Just going to have a dipstick and a gallon of spare while I get used to it!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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MikeR
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| posted on 12/1/06 at 11:48 PM |
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Naah, you'll just have your mobile and call either Chris or me begging we come out with a gallon or two of fuel.
Get some blooming LEDS in - weigh nout compared to that big fat engine and lardy a*se!
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Popee
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| posted on 12/1/06 at 11:52 PM |
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quote:
Originally posted by k33ts
the only reason i came up with this bodge idea is because there has already been a discussion on this forum about the safety aspect. ie messing with
electrical circuts going through the petrol tank.
i appreciate your help but to be honest after reading the discussion im to afraid to try it fryed chicken springs to mind.
it would only take a small mistake to make one hell of an explosion
I see your point,
How do you think the fuel is measured in the first place?
Lee
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NS Dev
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| posted on 13/1/06 at 12:04 AM |
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quote:
Originally posted by MikeR
Naah, you'll just have your mobile and call either Chris or me begging we come out with a gallon or two of fuel.
Get some blooming LEDS in - weigh nout compared to that big fat engine and lardy a*se!
How did you know about my refuelling strategy!?
Whaddya mean "lardar5e"
cheeky bleeder!!!
10 1/2 stone now matey!!!!!
Need to eat some more pies!
Retro RWD is the way forward...........automotive fabrication, car restoration, sheetmetal work, engine conversion
retro car restoration and tuning
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k33ts
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| posted on 13/1/06 at 12:15 AM |
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ive gota measure the resistance with a meter if u could translate that resistance to led's
i know alittle about electronics and to be honest didnt think it would be to much of a problem doing it
ive just taken my gauge apart two resistors going to a wound coil, that looks more scary
surely an electronic circut would be safer anyhow in my eyes anyway
westfields led meter and sender is just over £100
ill measure tmy sender tomorrow
doing searches harley davidson do a retro fit one aswell
ive used one for years but dony know. how does the multi meter measure it?
surely its the same sort of thing that we want to achive
[Edited on 13/1/06 by k33ts]
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02GF74
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| posted on 13/1/06 at 12:26 PM |
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can somoen put linky to the circuit?
actooally this is an ideal application for a PIC?
or can be done using comparators - how many LEDs to display range?
regarding electric current in your petrol tank; I've been trhouogh all of this, you tend to think about such things when you are sitting on top
of 10 gallons in a land rover!!
it isn't that much of a concern; petrol needs to be in the right properotion mixed with air to be explosive, if it burnt that easily, noone
would ever have starting or running problems!
also being volatile and having a vent, the air would get displaced by petrol putting the mixture into the non explosive tange.
you would design the circuit so that only low currents go trough the sender in case something goes wrong - usaully the fuel guage has high
resistance to limit current.
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tks
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| posted on 13/1/06 at 01:33 PM |
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yeah...
the trick is an pic
i would go for an
PIC818/819 it has an internal 8Mhz Osciliator sow less components are neded...
then you will need
4 1K resistors
1 7805
1 1uF cap
1 0,1uF cap
1 100uF cap
1 diode
5 leds would be enough??
5 resistors of 250Ohms (for the leds)
2 plane pots (to setup min level) and max level)
We will measure with one adc port the actual value readed.
with 2 others we will tell the pic our maximum and minimum level..of our sender....
its very easy and basic, sow the program
can be made easy and fast..
easy for a couple of pounds... its all done
Tks
The above comments are always meant to be from the above persons perspective.
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Popee
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| posted on 13/1/06 at 03:42 PM |
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Using a PIC is a bit overkill for a fuel guage isnt it?
Just use an LM3914, its a voltage to bargraph display driver! Fully configurable by a few resistors.
Use it to measure the voltage dropped across the sender unit, 1 chip, few resistors and 10 LED's and its done. Also has some nice features on it
too like dot mode or progressive, and a dimmer for the LEDS.
Lee
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k33ts
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| posted on 13/1/06 at 05:30 PM |
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took some measurements of current fuel sender one of etb instruments items £16ish
float at bottum tank empty 260 ohms
float at top tank full 35 ohms
which equates to voltage measurements at sender with fuel gauge connected.
3.492v empty
3.320v 1/4
2.973v 1/2
2.399v 3/4
1.663v full
although i dont know how to doit i cant see it that hard to trigger say 5 leds from this
if some one can design it i'll be the gineau pig as iknow a lot of people wuold be interested and could use an idea like this
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MikeR
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| posted on 13/1/06 at 06:02 PM |
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I'd like to now re-iterate the bit about volts and restistance. Can't remember who was asking but that perfectly describes the issue -
volts go through the fuel tank.
Ok, its pretty safe to assume this will be ok but if we get it wrong ......
man, did you see that car, it went like a bomb!
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tks
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| posted on 13/1/06 at 07:21 PM |
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Electrnoics
Yes its true,
an PIC is overkill but its cheap and its FREE.
Ok, make than the bloody sheme if its sow easy.. 
Tks
The above comments are always meant to be from the above persons perspective.
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Popee
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| posted on 13/1/06 at 07:29 PM |
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Current flows through the sender, and the voltage is dropped across the resistance!
The circuit I will design will not put any more load on the sender guage, i.e it will be passive!, you can use it in conjunction with an analouge
meter fuel guage or you can replace it with a resistor of the same value, ive got the circuit here, just need to do a few calculations, It can all be
done for under a tenner too, and u can have anything from 1 light to ten lights to show fuel levels.
Lee
Lee
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MikeR
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| posted on 14/1/06 at 10:43 AM |
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Lee - i want your babies.......
(to hold them hostage till you produce the circuit diagram - what did you think i meant?)
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Syd Bridge
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| posted on 14/1/06 at 03:05 PM |
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It is not uncommon in certain applications in particular cars, to use one sender, and use op amps wired to run as voltage followers measuring the
voltage drop across the sender, then send the output of each opamp to the gauge or daq.
This is not a big deal with any resistive/variable resistance sender, whether it be measuring fuel quantity, temp, or pressure; as long as the end
result is correctly calibrated. You can even amplify +/- to achieve the required range.
Make sure that the voltage supply to the sender is properly regulated, and use large capacitors to cut out RF interference.
The whole lot; opamps, resistors, capacitors, and a piece of perforated copper circuit board would total only £2-£3, from Maplins, RS or Farnell.
Syd.
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JoelP
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| posted on 14/1/06 at 03:22 PM |
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if you solder your connections properly and use a manufacturers sender, there is no chance of an explosion. At all IMHO.
Ive tried lighting my hob from a 12v spark, it proved impossible, and proper electrics doesnt spark or even get hot. (the resistor might get warm i
suppose...)
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