zim Posted June 12, 2012 Share Posted June 12, 2012 Morning, This is the job : I don't have a fuel gauge in my aluminium tank. So it's a bit of a guessing game about how much fuel there is left. We've run out in the far corner of Walters Arena before and this weekend we were pretty low on the Scotia Challenge - again a massive site ! I've found a sender unit from a bike that has 2 float switches in it. 3 wires. So I'm assuming 1 is common and the other two wires are NO if there is fuel present. NC when the level drops below. Object : I wish to have 1 led on the dash. That when the fuel gets to low it flashes. Then when it gets to very low it stays on solid. What's the simplest way ? I've tried searching google but once they all start talking about 555, transistors, resistors, nun sisters , capacitors etc I get a bit lost ! Si ? Gordon Quote Link to comment Share on other sites More sharing options...
cosecon Posted June 12, 2012 Share Posted June 12, 2012 Hi, about blinking it would be a bit more complicated (resitors, 555 whatever....) What about if you installed a dual color led : 1. low is green color 2. low low is green-red... Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted June 12, 2012 Share Posted June 12, 2012 Or a bit of a left field one, disassemble a rear LED bike lamp (from a pound shop!) and try and work out which track requires a poke to get it flashing, and which to get it on solid. The whole circuit is there for you already, for a pound Quote Link to comment Share on other sites More sharing options...
zim Posted June 12, 2012 Author Share Posted June 12, 2012 Right, i'll take a guess. http://www.555timercircuits.org/ There are a few circuits i've found like this. Would i be able to remove the potentiometer and use my level switch in place. In the low position the first circuit would be closed, so if i had a resistor in series (value to be calculated) it would blink. Then when the second switch closed (i.e. both closed), it would also have a resistor in series. Now there are 2 resistors in parrallel....Changing the overall resistance and changing the rate at which the LED blinks - i'd be able to adjust accordingly till it was too fast for the eye to see a blink and rather looks solid. (or maybe it'll be solid first then blink when low not sure if a decrease in resistance would speed it up or slow it down ?) G Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted June 12, 2012 Share Posted June 12, 2012 T = RC, so smaller resistor or capacitor will speed up the blink time. Short it and it will run infinitely fast, I forget the limit of a 555, but probably 10MHz ish. Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted June 12, 2012 Share Posted June 12, 2012 I stuck a load of LEDs on my dash on the SJ to tell me things, fine in the workshop but you can't see them very well on a sunny day. To stop me forgetting to turn the fan back on after wading i ended up with an LED telling me when the temp sensor was high so I knew that the fan should be running which half the time I couldn't see and a buzzer which sounded if the temp went high but the fan was turned off to remind me to turn it back on. Maybe you could do something similar for low and empty? Quote Link to comment Share on other sites More sharing options...
zim Posted June 12, 2012 Author Share Posted June 12, 2012 I like the above 2 ideas, simpler than mine. Fair point about not being able to see the LED. Hmmmm...... (Edit : could a mod, correct my spelling mistake in the title of Blinking). Quote Link to comment Share on other sites More sharing options...
robertspark Posted June 12, 2012 Share Posted June 12, 2012 Zim, I wouldn't fuss with a 555 timer IC, it is over complicated for what you need (if you still want a blinking LED that is....), buy a 12v blinking led: http://www.ebay.co.uk/sch/i.html?_nkw=12v+flashing+led&_frs=1&_trksid=p3286.c0.m359, I'd search for a superbright LED (or cluster) The 555 is a very simple IC, only a few components and they are very cheap and you could wire up one with a piezo buzzer to give you a buzzer tone, but you could just buy a 12 buzzer.... 2 wires, + no solder time, no issues with trying to locate a mini circuit board / a bit of breadboard, + making sure it's insulated etc. 12v Buzzers: http://www.ebay.co.uk/sch/i.html?_nkw=12v+buzzer&_sacat=0&_odkw=12v+flashing+led&_osacat=0&_trksid=p3286.c0.m270.l1313. Quote Link to comment Share on other sites More sharing options...
FridgeFreezer Posted June 13, 2012 Share Posted June 13, 2012 Can you not drill a 2nd 5mm hole and just use a 2nd LED? Quote Link to comment Share on other sites More sharing options...
simonr Posted June 13, 2012 Share Posted June 13, 2012 Why don't you just use a flashing LED? (LED's with the flasher built in) http://www.maplin.co.uk/search?criteria=flashing+led For example. If you are worried about not seeing it in sunlight, mount it in a shallow tube so it's recessed into the panel. I would be inclined to go for a flashing LED for mostly empty and a buzzer for very empty. I personally like these: http://www.maplin.co.uk/miniature-buzzer-3213 as they are loud enough to be heard but not annoying enough to make you smash it with a hammer! Si Quote Link to comment Share on other sites More sharing options...
dave88sw Posted June 16, 2012 Share Posted June 16, 2012 have a look at the specs for the led's too, i bought some 12v ones to go in mine but they blew every time i started the engine cos they didnt like the 14v my alternator was kicking out. Some are fussier than others but i just used a cheap voltage regulator off ebay. Quote Link to comment Share on other sites More sharing options...
Bowie69 Posted June 16, 2012 Share Posted June 16, 2012 A resistor would be the solution to stopping the LEDs blowing, even cheaper, less than pence! Quote Link to comment Share on other sites More sharing options...
zim Posted June 16, 2012 Author Share Posted June 16, 2012 My plan seems to have a problem. The senders that i've got aren't just a simple make / break switch. Both in and out of fuel they are about 1.4k ohm. Need to sit down and have a fiddle with them and a meter. G Quote Link to comment Share on other sites More sharing options...
elbekko Posted June 17, 2012 Share Posted June 17, 2012 Try to find the spec sheet for it, most likely it needs to be calibrated first. Quote Link to comment Share on other sites More sharing options...
Cynic-al Posted June 18, 2012 Share Posted June 18, 2012 If the resistance is up and down you could use that with a 555 to alter the flash rate... or http://www.cbsonline..._Gauge_Kit_FUGA ? Quote Link to comment Share on other sites More sharing options...
pete3000 Posted June 19, 2012 Share Posted June 19, 2012 have you got a pic of the sender unit. One is likely to be resistance for level whilst the other is probably a low limit n/o switch for low fuel. Re: your flashing (low) solid (really low) . Why not get a flashing superbright red led and a solid superbright red led, push them into the same panel lamp housing and voila multi use led. When power to flashing only it will flash, if you apply power to solid it will be solid anyway even if flashing is still errrrrr flashing. common the cathodes (ground) and put a resistor on each anode leg back to inputs. Vary the brightness by altering the resisitors slightly, say 1.8k for flash and 1.5k for brighter solid (brighter 1.5k and 1.2k) etc. Pete Quote Link to comment Share on other sites More sharing options...
A Twig Posted June 19, 2012 Share Posted June 19, 2012 Really easy option if you really CBA to do any design or assembly, copy this: http://www.hobbytron.com/vmk102.html Simply swap one of the pots out for the signal coming from your sender. Proper job! Quote Link to comment Share on other sites More sharing options...
A Twig Posted June 19, 2012 Share Posted June 19, 2012 Unfortunately my PC with all my design software has gone bang, but on a couple of months time when its up and running, if you're still having problems I'll post up a decent solution! Quote Link to comment Share on other sites More sharing options...
robertspark Posted June 19, 2012 Share Posted June 19, 2012 Zim, You could use a transistor, and a couple or resistors, such as the following circuit: http://www.kpsec.freeuk.com/images/tranldr2.gif Basically you substitute your the LDR (Light dependant resistor) for your analogue fuel signal, and adjust the level setting via the 10K potentiometer.... What you are doing is switching the diode on and off at the setting you want. Measure the fuel level sensor resistances at full, empty and mid point Note: don't think the ciruit will work with a buzzer..... as it needs a bit of a load, and I'm not sure how it responds to flashing LED's and you are basically switching the bias on the transistor collector. But for a couple of £ it's worth a try in my opinion, and it can be made small enough to seal in resin, in something such a small pill container and made IP rated (landrover waterproof). Hope it helps Quote Link to comment Share on other sites More sharing options...
GW8IZR Posted June 20, 2012 Share Posted June 20, 2012 Tank sender normally goes to ground via resitor so above circuit would need a change, you ought to be careful poking 12v into the tank - make sure your circuit limits the current under fault conditions. Quote Link to comment Share on other sites More sharing options...
robertspark Posted June 21, 2012 Share Posted June 21, 2012 You can reverse the above circuit around, using a PNP transistor, instead of an NPN transistor.... Basically you swap the V0 and V+ over, and swap the transistor for an PNP type.. Very very simple change, if anyone is interested I'll search for the alternative circuit drawing. (Well spotted GW8IZR)... Limit the current with a fuse.... or you could use a voltage limiting chip (3 pins, can't get it wrong.... Live, Ground & Out) ---- any variety of LM7912 (12v) You can use them to provide up to 1A at a regulated voltage.... http://www.hep.upenn.edu/SNO/daq/parts/lm7915.pdf They don't provide over-current protection (so can go pop), but are cheap If you need an all singing and dancing voltage regulator with overload protection, the one I use to use was a L200 is one to start with (http://www.datasheetcatalog.org/datasheet/SGSThomsonMicroelectronics/mXxzqr.pdf) but it has 5 pins and requires a few more components... bit of overkill for a simple circuit. Note, circuits get updated and change over time, so there may now be alternatives can be sought that do exactly the same thing. Zim is a bit busy on other things..... he did a bit of damage to his front axle so I think this has gone on the back burner for a little while.... Quote Link to comment Share on other sites More sharing options...
zim Posted June 22, 2012 Author Share Posted June 22, 2012 Zim is a bit busy on other things..... he did a bit of damage to his front axle so I think this has gone on the back burner for a little while.... Damage...pah...i only wrote off an ARB, pegged housing and HD R+P ! I'm currently out at sea, will worry about this when i'm home next month. Cheers for the replies though, i'll have a fiddle at some point. Quote Link to comment Share on other sites More sharing options...
fozsug Posted June 22, 2012 Share Posted June 22, 2012 Damage...pah...i only wrote off an ARB, pegged housing and HD R+P ! We need pictures!!! Quote Link to comment Share on other sites More sharing options...
zim Posted June 23, 2012 Author Share Posted June 23, 2012 if you look closely you can see the small section of stripped ring gear & pinion. if it hadn't been pegged then i think more of the ring gear would have been stripped. i think the ARB let go and nothing was wrong with the cw+p. the pegged part worked well also, no complaints there. new stuff on route from ashcroft soon G Quote Link to comment Share on other sites More sharing options...
fozsug Posted June 23, 2012 Share Posted June 23, 2012 if you look closely you can see the small section of stripped ring gear & pinion. if it hadn't been pegged then i think more of the ring gear would have been stripped. i think the ARB let go and nothing was wrong with the cw+p. the pegged part worked well also, no complaints there. new stuff on route from ashcroft soon G Good job! Quote Link to comment Share on other sites More sharing options...
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