DIY-WB LED problem (KC-5300 display)

[Crescent Kao]

Any other suggestions on how I can diagnose the problem with the LED
display? I'm stuck. Thanks.


Crescent Kao
Director of Marketing and Sales
www.c-speedracing.com


----- Original Message -----
From: "Peter Gargano" <peter at techedge.com.au>
To: <diy_efi at diy-efi.org>
Sent: Sunday, January 20, 2002 4:39 PM
Subject: Re: DIY-WB LED problem (KC-5300 display)


> Phil Hunter wrote:
> >
> > Looking briefly at the schematic, here's my suggestion: remove
> > IC1 from it's socket, nothing to the sensor input, on IC2a short
> > pins 1 & 2, this will make it a unity gain buffer where pin 1
> > follows the voltage on pin 3.
>
> IC2a functions as a comparator feeding into a simple digital input
> at RB0. RB0 cannot be made an A/D input (there isn't one on the 16F84)
> and the software does the A/D conversion.
>
> > Vary VR3 from end to end, pin 1 should
> > vary from about 1/4 to 1/9 of 2.5V. Remove the short and jumper pin 1
> > to the sensor input, this will turn it into a 3X amplifier, now
> > varying VR3 should have pin 1 varying from 3/4 to 3/9 of 2.5V. This
> > should give you confidence that all the input circuitry (with the
> > exception of VR2, the 3.3K & the 560K ) is correct.
>
> The PIC's (IC1) RA3 output produces a PWM signal that appears as a
> voltage on pin 3 of IC2a. It's compared with the voltage from the
> sensor in a successive approximation fashion to produce a firmware
> 8 bit A/D converter. Any kind of serious testing probably requires
> a 'scope, but I've used one of the sound card input attenuator boxes
> and CoolEdit to see that everything is working as it should.
>
> Make sure IC2b (in the same package) is working by adjusting VR1
> (the light/dark auto-control preset) to dim the display - if it's
> working okay then IC2 is probably working - if not ....
>
> Peter.
> --------------------------------------------------------------------------
--
> To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the
quotes)
> in the body of a message (not the subject) to majordomo at lists.diy-efi.org
>

----------------------------------------------------------------------------
To unsubscribe from diy_efi, send "unsubscribe diy_efi" (without the quotes)
in the body of a message (not the subject) to majordomo at lists.diy-efi.org