Speed controlled on/off relais

[alec_t]

I now even can set to fan to start at 30 km/h and by another setting to stop at 90 km/h, super !

Not quite. The maximum hysteresis is 24kph, so if the fan turns on at 30kph it would turn off at 54kph max. To get it to turn off at 90kph it would have to turn on at 66kph.
If you need performance beyond what my circuit provides, without more complexity, then a microcontroller-based approach might be better.

 

[Edce]

Maybe I was to early to conclude that the setting of the speed potmeter at 67 and the hysteresis at 24 the fan can stop at 90 km/h. I don't need in fact stopping higher then 60 km/h.

 

[alec_t]

setting of the speed potmeter at 67 and the hysteresis at 24 the fan can stop at 90 km/h

That should be possible, but it's not what you said in post #20 .

 

[shortbus=]

So its not the oil directly which has to be cooled.

I misunderstood what you were doing, thought you were cooling the oil in a cooler. But the same could be done for the cylinder heads just put the sensor for the fan on the head fins. What type of car is this?

 

[Edce]

The engine is a Citroen Visa engine. Its purely air cooled. The engine is exactly of the same construction as the famous BMW boxer motor (motorbike). However BMW added fluid cooling and a fluid radiator with a fan. The specification of the bike actually says that the fan is only for slow driving (city and hot weather). So that would be also the best solution for my Visa engine, but there is no internal structure where the cooling fluid could come close to the engine oil. Putting a sensor to the cyclinder heads is a possibility which is not regarded yet. Of course the heads become very hot and the temp limits there are not known yet.

 

[Edce]

So next is that I have to figure out what to put where. The distance from the fan to the dashboard is about 1,30 m. I also have to keep the elec. components coolest possible. So I will need quite a length of wiring.

 

[alec_t]

I've been tinkering with the post #19 sim to widen the hysteresis range. Optimum values for R6,7,8 seem to be 47k, 47k, 150k respectively. These give a 20-44 kph hysteresis range. With that range, the SetSpeed pot can cover a cut-in speed range of 20-68 kph.
Did you get the sim to run? The file locations I specified apply if your OS is Windows10.

 

[Edce]

Many thanks for the update. Once I am in the fase of testdriving I can decide what best suits the purpose.
I apply Windows 10 but I did not get it working yet. I did not find the relay symbol yet as well.

 

[alec_t]

I did not find the relay symbol yet as well.

In the zip I posted there is a folder named "Relays". If you copy that into LTspice's asy folder it should show up when you click the "Component" button.

 

[Edce]

Alc_T : I cannot manage the circuit to start "running". Would it be possible for you to film your screen and post a you tube item ?

 

[alec_t]

If you're expecting an animated display, then LTspice doesn't do that. Just click 'Simulate/Run' and you'll get a blank plot window. Then left-click a component symbol to get a plot of the current through that component; or left-click a circuit node to get a plot of the voltage at that node.

 

[Edce]

Alec_T : now I get a lot of e-mails from forum members of LTspice. How can I avoid getting these further ?

 

[alec_t]

This may be shutting the stable door after the horse has bolted, but have you tried adjusting your Privacy etc settings on the site originating the e-mails?

 

[shokjok]

Have you considered a slide switch attached to the accelerator pedal feeding a voltage comparator circuit to activate the relay feeding the blower fan when the speed is above 40 km/h?