led fuel indicators wvo tank

This is for a two tank WVO (waste vegie oil) system. I desire a flashing LED on the WVO tank sender @ output of 0 ohms and off @ roughly 50 ohms and another flashing LED @ 200 ohms. The problems I'm trying to overcome are: 1: overfilling by myself or failure of the return fuel valve (diesel return fuel routed to the wrong tank), 2: a flashing LED when WVO tank is near empty. I can adjust the sender float to read 0 ohms @ 1 gallon to allow for reserve & possible settled out water. Tank has baffles.

2003 VW Golf TDI

Thanks for the advise.

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Find out what voltages they correspond to. You then use 2 comparator circuits - one for each LED (and add a flasher circuit or use flashing LEDs). The "voltage" comparators can be done countless way - quad comparator chips (LM3900 etc), Op-Amps (I prefer CompChips!), even discrete components and uPCs. Also check regulations. Some stupid regulations require ignition to be off (thanks to handbags!) and that may mean or imply fuel-tank un-powered whilst refilling.