How to read Speedo at low speed

[Acetronics2]

The problem I have is the pic has to act quickly, the engine revs very quickly, and if it spends 1 second counting pulses, it will probably be over-revving by then.

Of course, at 1 kph, the pulse period is 2.2 seconds, and that's how often you can update the display. But at 1kph, you don't need a faster refresh.

Hi, folks ...

Problem is Here, not a display problem ...

You need quasi " real-time updated speed " ( Cf Post # 2 ) ...

Alain

PS, Don't tell " Davewanna" , BUT

"Dave would have liked to" ... Humour !

[Darrel Taylor]

Problem is Here, not a display problem ...

You need quasi " real-time updated speed " ( Cf Post # 2 ) ...

I've tried ... but I don't understand what you mean Alain.

He's reading the Speedo.

If the engine revs fast, then so will the speed sensor.
And you'll no longer be going 1kph.

BTW, where'd he go.
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[davewanna]

Sorry all! Something unexpected has come up over the last 2 days. I didn't realise I had this many replies! I haven't even had a chance to read over everyone's suggestions yet... I will go through it all and post again.

Very thankful for all the assistance!

Cheers
Dave

[Acetronics2]

I've tried ... but I don't understand what you mean Alain.

<br>

Hi, Darrel

At school, I just learnt to carefully read the Problem terms :

sampling every 100ms

The unit is based on a 16F877a running at 4mhz (I can run it faster if I have to) It also controls the air-conditioning & thermo fans in a climate control kind of way, aswell as having a 20x4 display that gives me info on engine stats and temperatures.

I do know forumers are not so clear in what they look for ... but I do whith what I have under the eyes ...

Regards

Alain

[davewanna]

Darrel,

From your advice I guess my quickest easiest way of making this work is with pulsein (seeings I have very little interrupt knowledge yet)

My reference to 21kph was if I use COUNT to count pulses over a 100ms period.

I will try this in the next few days, with a pulsein timeout period of about 200ms (to prevent all the other functions from slowing down too much.)

I still haven't had enough time to go over what everyone has posted. But rest-assured it is appreciated.


Thanks!