Non Destructive testing (letting the smoke out)

[Sandy]

The problem is that if you have a hold current of 1 amp, and the each of
the injectors takes 1 amp, the drive will hold the current at 1 amp, even
if their is a dead short (until the drive smokes). So will not work very
will. I slipped up in the comment on the first email about adding saturated
injectors, it still will not work. Peak and hold drivers work something
like this, it dumps the full voltage current into the injector, since the
injector is around 2 ohms, you get a very fast reaction, but the current if
left on for very long would smoke the coil, so after the initial quick zap,
the current is reduced to a safe level by some feedback that has a fixed
value, might be 1 amp, so as you add more injectors in parallel the current
will hold at 1 amp, and each injector will be getting less, in the case of
2 injectors, each would get 1/2 amp hold.  Saturated injectors are
basically a switch, so you can (within limits of the device) add additional
Saturated injectors.

Yes, pretty much 3 15 ohm injectors will look like one 5 ohm. BUT if you
are driving them with a satruated type, the power problem will not be that
bad, as the transistor is operating like a switch the  amount of power that
is dissipated in heat will be much much less then a saturated type. You
will still need to check for over heating as it may be designed with
minimal heat sinking, but you could easily fix that! Again as long as the
drive can deal with the extra current, you should be ok, just need to get
rid of the extra heat

Sandy


At 03:43 PM 1/12/99 -0500, you wrote:
>
>What would be the effect of placing 3 saturated type 
>injectors in parallel on one peak-n-hold driver?  
>
>Will the peak function of the peak-n-hold driver be 
>of benefit to opening the saturated injectors?
>
>Do three 15 ohm injectors in parallel look like one 
>5 ohm injector to the driver?
>
>TIA,
>-Mike
>
>-----Original Message-----
><<Saturated (15ohm) injectors will, and it just depends 
>on the current capability of the driver>>