Run out of outputs

[Steve001]

Just a quick update,

not sure whats happening yet, going to look into it a bit further later on.

the circuit works i can see the outputs 0 , 1 pulsing ok up to the filp flop
if i connect the led eblock onto the output i get no output . However if i fit my logic clip to the ic i can see the outputs flashing nicely .
if i connect my lcd display board nothing happens, i lose the outputs ( this was checked on verified on a scope)

will let you know what i find

Steve

[Steve001]

Really stuggling on this one, and at a loss of what to do now

i have built the circuit as the attached drawing.

using a pic 16f877 i/p with my circuit connected to port B if i connect the LED e block to port B i can see the leds flashing nicley
if i connect my made up circuit to port b and the led e block to the output i get no outputs.
if i connect a logic clip across the 74HC05 ic my circuit works
Logic clip is a ryley automation HP548A
i have tried pull up resistors (4k7) on the outputs of the 74HC05 still no output
tried pulling down with the same resistors 74HC05 still no output

messuring the resistance of the logic clip showed a resistance of 1m6 to the ground pin, grounded the inputs and outputs of 1 gate to test - no output
so obviously there is somthing a bit more suttal in the logic clip to make things work ? ( diodes de coupling caps etc ?)

leaving the logics clip on my circuit so things work , if i connect my 4 x 16 display e block that i made, which has been proven to be working
results in a blown flip flop chip

looking at the data sheets on the pic the output current is 25Ma. then looking at the lcd dispaly the current is 1.2 Ma on each data line the data sheet on the flip flop states 0.1 Ma hence the blown chip.
So to increase the drive which is the best way to go ? More 74HC05's or ULN2003AN or is there somthing better ?

Benj ,
your circuit looks to be working is that the same display on the e block pcb ? how much current dose that draw on data lines ?
did you have to do anything different to get your display to work ?

Totally lost now

Steve

[medelec35]

Apart from my suggestion of 74HC595, in a previous post, what about an additional small cheap microcontroller, using internal osc and MCLR disabled?
The microcontroller can take a serial i/p on one pin, convert this serial i/p to a byte variable and using the LCD component and an o/p port to drive your LCD.
I would guess A 14 pin microcontroller will do the job nicely, and would be less hardware involved.

Martin

[Steve001]

just to say that i am working now , Made a couple of schoolboy errors

had to link GND pins near the 9 pin d plug and socket to the ground power strip ?
( I know that they are linked via the ground plane on the pcb )

attached is circuit

many thanks to all that helped me Benj , Malcom , Trevor and others

Steve

[szamy]

Hi All,

Somebody try this project ? http://www.romanblack.com/shift1.htm
Maybe have someone FC LCD Macro for this Shift1 project ?
I think, this is a very usefull thing , but i cant find FC Lcd macro for this.

(sorry my english)

Szamy

[Benj]

Hello,

The idea looks good. However adding all that circuitry around the PIC just to save 1 I/O pin seems a bit strange. Also the software becomes a lot more complicated to program. You could have a go at changing the PIC_LCD.c component C file to allow it to perform this one pin LCD function.

delay functions look like this.

delay_us(1);
delay_us(15);
delay_us(200);

That should give you all the delays specified on the webpage.
Let us know how you get on.

[szamy]

Hi Benj,

thanks, but is chinese for me , i cant programming
i hope maybe someone have working FC lcd macro for this project . I have an electronic project, what have only 1 free output pin, and i like to use that for the lcd drive.(have much case , why so i need to use only these )
maybe the FC 5 will handling DS2408 ?