LED Temperature Display - Get Help Now!

Hi tech enthusiasts,

I am looking for a way to create a temperature display.

The system is based on a PT100 sensor and a few LEDs. The supply voltage is +12V DC.
The temperature range extends from +50°C to +300°C.

The goal is to have an LED light up at 50°C, a first and second LED light up at 100°C, three LEDs light up at 150°C, and so on.
Now I'm looking for a circuit that can do that.

The problem for me is that the PT100 outputs variable resistance values. However, the LEDs require fixed values (20mA, 0.7V) to operate and avoid being overloaded.

Does anyone have anything for me?
Thank you for your help.

cu smith2

It might not be the right forum for this.

Take a look at the datasheet for the LM3914. You might be able to accomplish what you need using that.

might not be the right forum for that.

Take a look at the datasheet for the LM3914. You might be able to accomplish that with it.

Hi,

The idea with the LM3914 is good. However, wouldn't it be more sensible to use a small LCD panel meter to display the temperature more accurately? There are such displays available online for under 10 EUR, and they often have backlighting.
What are you planning to do with that device? Are you going to measure the temperature inside the exhaust pipe?
'50-300°C is quite a strange range...'

Greetings.

Eike.

@eike

I also prefer a digital display to a light bar. While my experiences with the a277 (formerly the East German equivalent of the LM...) were generally positive, it wasn't suitable for precise measurements.

but it wasn't asked about lcd...

Use operational amplifiers as comparators connected to various reference voltages.

Use operational amplifiers as comparators connected to various reference voltages.

Or, as mentioned above, use the LM3914. It already includes everything you need, with an additional LED driver and is pre-calibrated...

Whether it's an A277 or an LM3914 doesn't really matter; @Eike's suggestion is actually better.

What's important is that the temperature sensor, within the specified range, provides the desired measurement/resistance curve and can also withstand the conditions.

It doesn't make sense to replace the heating element before every trip.

The measured values are the result of a purely ohmic voltage divider and are only evaluated and displayed as values by the ICs.

Whether it's an A277 or an LM3914, it doesn't really matter; @Eike's suggestion is better.

What's important is that the temperature sensor, within the specified range, provides the desired measurement/resistance curve and can also withstand the conditions.

It doesn't make sense to replace the heating element before every trip.

The measured values are the result of a purely ohmic voltage divider and are only evaluated and displayed as values by the ICs.

Okay, and what should this thing display? It's clear that it should show temperature, but where should it be measured?

Eike.

Hi everyone,

Thank you for your suggestions. I have implemented a circuit using the LM3914.
I want to measure the temperature using a PT100 sensor because its linearity is unmatched.
Where is it measured? Hmm, I know this is the wrong forum, but I was sure I would get a technically sound answer here. It's on a cylinder head.
I'm just saying: 2-stroke, SuperPlus, Castrol A747, 70cc, 11 horsepower, 10000 RPM.

Please don't be mad at me.

Thank you for your help.

cu smith2

Hi @all,

Thank you for your suggestions. I have implemented a circuit using the LM3914.
I want to measure the temperature using a PT100 sensor because its linearity is unmatched.
Where is it measured? Hmm, yes, I know this is the wrong forum, but I was sure I would get a technically sound answer here. It's on a cylinder head.
I'm just saying: 2-stroke, SuperPlus, Castrol A747, 70cc, 11 horsepower, 10000 RPM.

Please don't be mad at me.

Thank you for your help.

cu smith2

Oh, so it's about a chainsaw. Who would have thought that ?

Hi,

What is that, a styled Simson with a "piston failure warning bar display"?


Best regards, Rainer.

No chainsaws, and definitely no 'piston seizure warning bar display.'
Just a simple display showing the cylinder head temperature - that's all.

Regarding the vehicle being used, I'll leave you to speculate further...


cu smith2

hey hey...

Simson and piston seizure? I haven't even managed to get that with my many S51s...

'He spoke, the one who lives in the homeland of the Simson Mockicks...'