MC3334 question

[sandy]

At 09:55 AM 3/6/96 +1000, you wrote:
>Pardon my ignorance, but I am a computer programmer and my knowlege of
>analogue is _very_ limited....
>
>On the MC3334, when used to drive an MJ10012 (?) with current sense, the
>circuit diagram I have shows a .027 Ohm resistor bewteen ground and the 
>MJ10012, with the sense taken from the MJ10012 side. In Tim Drury's article
>on Distributorless ignition, he gives a circuit for the ignitor which does
>not have this resistor. I am assuming the resistance is necessary for the
>current sense to work, - so what can be used to create this resistance, or
>can it really be discarded (as per Tim Drury's design)?
>
I don't have the circuit handy (i'm on the road), but I thought that it had
the sense resistor. The value on the moto data sheet is .075Ohms I think.
Their is also a variable resistor from that to form a simple divider network
that is used to adjust the current that the limiting starts at. The thing
that I remeber from Tim's stuff is that it was the exact same circuit as the
moto data sheet. 


>Also, how do you pick a coil to work with this design? Most coils I have
>seen (single output) are sold with no info on resistance. Can the M3334 (when
>used with current sense) use _any_ coil? I am currently using a coil with 
>a ballast resistor and would prefer not to fork out another $50 Australian
>for another coil :)

The above mentioned setting of the variable resistor will set the maximum
current that the coil is driven to.

Sandy
**********************************
Sandy Ganz        sandyg at visix.com
Visix Software Inc. 
**********************************