Possibility of picaxe as Degrees rotation display

[bluejets]

Presently working with others on pic ignition.

Thought i'd try to do my bit with a degrees delay LCD readout and thought I'd ask here first to see if it is feasible with picaxe.

Thought was take existing pulse input from hall effect and from existing micro delay output, store the time and compare with rpm to give degrees delay and then display on an LCD. Possible...???

 

[AllyCat]

Hi,

It's possible with a base PIC chip and perhaps within PICaxe Basic by using "advanced" control of the raw hardware (POKESFRs, etc.). But probably the easiest method is to use a small amount of external "hardware assistance" (a flip-flop or perhaps a few gates).

AFAIK the problem using (only) PICaxe Basic is that the only measurement which is fast enough is PULSIN, but that only reads one pin, it cannot measure the time between two events on different pins. Which PICaxe are you considering? Also, what is the minimum "angle" you need to measure (it might be easier to do if it's > perhaps 10 degrees).

One solution would be to use an external Set-Reset flip-flop (sadly the SR flip flop on most(?) PIC chips appears to have only one input). The Hall device would trigger one input (e.g. Set) and the "micro delay" the other input (e.g. Reset). The output from the FF should give a square wave which can then be measured with two PULSIN commands. Alternatively, connect a low pass filter (R + C) onto one F-F output and read the analogue value, which could give a direct "angle" reading (angle = A/D * 360 / 256) assuming that the flip-flop gives a rail-rail square wave output.

Cheers, Alan.

 

[rossko57]

Are we talking about a spark ignition engine? The usual measurement of interest is degrees of advance.

If there is a PIC driving the system and already doing all the donkey work timing and maths, can you get it feed data out so that your Picaxe only has to format and display the data? Or is your part of the project required to do actual measurements as a check on the rest?

 

[bluejets]

There is much happening with the original unit so my thought was to attack it independantly.

OK...looks like not possible .....Thanks

 

[hippy]

OK...looks like not possible .....Thanks

I think that's a bit premature. It might turn out to be impossible, but we haven't even had full details of the setup and requirements so far. Plus no one said it wasn't possible