Re: Problem with PIC & LCD display

In message <nc9k14l01uogp0gptq4rgqldglvjkn17nt@xxxxxxx>, Spehro Pefhany <speffSNIP@xxxxxxxxxxxxxxxxxxxxxxx> writes
On Thu, 1 May 2008 21:08:07 +0100, Steve H <steveu@xxxxxxxxxxxxxxxx>
wrote:


Have no photo to hand and the equipment isn't with me just now. Fully
assembled it comprises the PIC with LCD, 4 control buttons and several
logic inputs/outputs, four of which control 4 to 16-line latches that
switch solenoids via darlington drivers. The unit is part of a gas
sampling multiplexer system.

Is it the solenoids that are mucking things up?

No, I should have pointed out that the solenoids are not operating in the state I'm testing it in. They will be either disconnected or a pair of them will energise at power-up and remain in that state throughout, depending on which bits of the unit I have plugged together.


Currently, a lot of the circuitry is disconnected - there are 3
individual PCBs (etched boards). It's working in a bare-bones sort of
state at the moment, pretty much the PIC and display only

Lash-ups tend to be more sensitive to EMI.

I know what you mean, though with this project there are 3 boards connected via ribbon cables. I can disconnect the output logic and solenoid circuitry by disconnecting the ribbon connectors on the control board. It is thus a reasonably 'clean' way to run only the control board.


An earlier version of the device, identical but utilising in place of
the 16F877A/LCD a pair of 16F84As and driving a 2 x 7segment LED
display, has worked in the field flawlessly for 3 years.


Best regards,
Spehro Pefhany
Best regards,
Spehro Pefhany

--
Steve H
.

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