Not sure how to go about, or the easiest way to accomplish this.

My goal is to have a red LED light up bright when my Motorcycles ECT (engine coolant temp sensor) is showing a high temp.

The ECT (engine coolant temp) sensor is speced to show 2.1k-2.8k ohm at 86f, and show 0.65k-0.73k at 248f. I still need to test MY sensor to see its EXACT ohm load when its at around 240-250f+, but whatever ohm load that is, I'd like an LED to light.

I don't want an led that slowly brightens as the bike heats up, I only want this as a warning light, to know when I'm too hot.

I'm not completely knew to circuits, I can half ass read schematics, and I repair electronics for friends/as a hobby. But creating a circuit like this, I am completely lost.


/back story to me wanting this circuit. I'm building this bike for parking lot stunt riding only, no gauge cluster. I'm re-doing the wire harness, ditching all the stuff I don't need (turn signals, horn, kick stand sensor, brake light switch, etc etc), and adding stuff that I want specifically to keep my bike safe and to help with my riding style. I'm going to be running a red led off the oil pressure sending unit, a led for my check engine light, a led for my neutral sensor, and a led for low fuel. Those were easy.

Sorry if I postedin the wrong section. I've been lurking the forums learning more about circuits over the last few months.

To give you an idea my bike I'm building, first pic is how I bought the bike. Second pic is from tonight after I Tore it down, did repairs, maintenance, cleaned, prepped, painted, and mods currently being done and more to be done as money allows.

 

Really, if it is a easy circuit with few components that can be easily changed for different resitances (that hopefully I have spare parts laying around to make without waiting to order stuff), I'd likely end up wanting to have two separate circuits.

One to light up say a yellow led when the ECT is sending whatever resistance it will show when my bike is in the 210-230ish range, and a red led to only light when my bike is showing over 240f.

I still need to test my ECT to see exactly what resistances it shows in the temp ranges I want. All I've tested so far is room temp, and its showing 2.2k ohm in my cold basement (prolly right around 66-68f right now).

 

Your easiest method is to use an op amp Comparator, like a Lm3914 and measure the voltage across the sensor. I would put a voltmeter across the sensor at cold, warm and hot, to see what range it gives you.

 

Not as much fun as building a circuit but coolant temperature switches like these would do it. Some are for warning lights, some turn radiator fans on.

Autometer Pro - Lite Warning Temperature Light Switch - 3247

FAE Coolant Temperature Switch - W0133-1790179

 

thank both of you for the help! The op-amp comparator sounds like the best option for me, considering I have many different types of spare op-amps laying around from class D and class Ab car amp repair, just need to dig around and see what I have, and research more to see what I can make work. I've never really "designed my own circuit" outside of very basic voltage drops, current limiters etc.

The bike has two factory coolant temp sensors, the ECT that I wanna use for reference that is mounted on the thermostat housing, and also single pin sensor on the radiator that is just there to turn the fan on when the bike hits around 210f by shorting to ground. .

my original plan was to just buy a cheap tiny led temp gauge with its own temp probe. Something like this
https://www.amazon.com/DROK-Digital...id=1527601271&sr=8-5&keywords=led+temp+sensor

But I really don't "need" to know the exact temp of my bike, I just need protection so I don't over heat it and not know until its too late. My bike will regularly see 220-230f water temps when I'm pushing it, which doesn't harm it. But without a cluster, I always fear me running it hard, and well past 250f, and warping my head/blowing my engine.