Mornin' all.

Spent a fun hour or so yesterday building my AFR meter. Seem to have done something wrong. The first (power) LED lights very, very dimly despite having 8 or so volts across it. Is that right? I guess the current is being limited by the chip drawing power...

Secondly, trimming up seemed a case of move one, then move the other, then move one and trial and error. Looking at the circuit diagram, that seems to be bound to happen, but it still struck me as slightly wrong.

Have I buggered something up, or is everyone's experience like this.

My power source is a 9V PP3 at the moment...

Cheers,

nick.

 

Nick,

Not sure about the power LED thing but the trimming is correct. I used a 12v transformer to power the circuit so that when I set it up, and moved it to the car, it would be the same. In that case I set the inputs to 700 and 900mV. I then used a 9V battery with a potentiometer to supply the input voltage to test that the LEDs all lit up in the range from 0-1V.

I don't know if that helps you at all?

Let me know if I can help further?

Ta,

Matt.

 

Nick, yes you expect one to glow dimly until you feed an input signal. When trimming up yes it is trial and error. This method with the chosen pots keeps the component count down. One seems mainly to set the offset between the two, the other shifts it, but they are clearly not independent.

 

Marvellous, I'll carry on then - thanks very much

The "right hand" pot seems to control the range of Ref lo to Ref hi, and left seems to set the start point. It was definitely a case of homing in on the target values.

Cheers again for your help, most appreciated. I'm only running 16PSI on my dawes / K&N / downpipe setup and want to see that everything's safe.

Trimming the dawes was fun too. Starting at 8PSI and working up... Anyone watching the ringroad near horsforth in Leeds (unlimited with a steep uphill, plus a very handy cut-through road to take you back to the bottom) must have thought "what is that nutter doing".

More flashing lights

nick.

 

I remember when setting mine up, I used a long North Circular slip road At the bottom there was a side turning and I went down there, round the block doing 30 warming down, back to the start of the slip road and into a car park at the top.

There was a guy sitting at a bus stop giving me funny looks as I'd arrive, idle for a min, turn off, get out, bonnet up, play, bonnet down, slip road, howl down the slip road and a couple of minutes later, I'd be back, doing the same

Once you have this up and running, you'll just need an inlet temps gauge m8

Matt

 

Down that way lies madness - I'd be convinced I needed FMIC