S8/F88 H-Bridge as Lambda Htr control

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tpepmeie
Posts: 10
Joined: Sun Sep 22, 2013 12:32 am

S8/F88 H-Bridge as Lambda Htr control

Post by tpepmeie »

Hello, all. I'm about out of outputs, with 16 Injectors/8 ignition coils. Is it acceptable to use one of the H-bridge outputs to control the lambda heater circuit (Blue wire on NTK L2H2)?

Second question, the pinout shows pins 75 & 76 for the Lambda ion pump. Is there any config necessary in SCal for these pins? I've already set Lambda 1 & Lambda 2 voltage to pins 18 & 45.

Thanks,
Todd
TimH
JT Innovations
Posts: 661
Joined: Wed Sep 01, 2010 2:51 pm

Re: S8/F88 H-Bridge as Lambda Htr control

Post by TimH »

Can't see any reason not to drive the lambda heater from an H-bridge: it's a 0-12V PWM drive after all, just active to 12V rather than the low-side-only of an injector output.

Don't set lambda voltage to those pins: just set the lambda input configuration to be UEGO and everything else is taken care of.
stevieturbo
Posts: 961
Joined: Sun Dec 07, 2008 2:04 pm

Re: S8/F88 H-Bridge as Lambda Htr control

Post by stevieturbo »

Not sure you could use the H Bridge as Lambda heater ?

Could you use another output instead and then use the H for something else ?

To use the H Bridge, surely you'd need to ground Blue, then apply the voltage to Yellow via the H Bridge ??

And not sure if there's anything more going on in the background with regards heater control but it would no longer be assigned correctly ? Defo one to ask Syvecs support.

Or run the second set of injectors batch fire to free up some outputs, or coils as a wasted spark type setup which would again free up some outputs.
TimH
JT Innovations
Posts: 661
Joined: Wed Sep 01, 2010 2:51 pm

Re: S8/F88 H-Bridge as Lambda Htr control

Post by TimH »

stevieturbo wrote:Not sure you could use the H Bridge as Lambda heater ?

To use the H Bridge, surely you'd need to ground Blue, then apply the voltage to Yellow via the H Bridge ??

And not sure if there's anything more going on in the background with regards heater control but it would no longer be assigned correctly ? Defo one to ask Syvecs support
A low-side drive is an active switch to ground. A high-side drive is an active switch to battery. A half-bridge (i.e. only connect to one of the H-bridge pin-pairs) has both switches. With the yellow wire connected to +12V, the H-bridge drive will be switching between +12V and 0V rather than open-circuit and 0V; the effect is the same.

There may be an argument to connect the yellow wire to ground rather than battery, so that if the half-bridge is "off" (rather than tri-state) and therefore at ground, there is no current through the heater; also the duty is more intuitive, with 0% meaning no pulses to +12V, therefore no current.

There's nothing going on in the background - the output will still be PWM controlled and follow the heater volts strategy set in Output functions, as long as you take care with the polarity of the output PWM as noted above.

Nevertheless, a quick email to Syvecs support would obviously be very wise :)
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