dual 7-segment countdown timer code

[dr.ragh]

well this is just an idea of the schematic, i have to add transistors to drive led display and for buzzer and 5w led

[T.Jackson]

well this is just an idea of the schematic, i have to add transistors to drive led display and for buzzer and 5w led

I see many similarities with Proton Vs PBP, and I also see many differences. I've personally never used Proton.

Give the Proton forum a go, if you don't have any luck there, perhaps I could give you some PBP code. This of course will need to be converted across to Proton.

Also I might add that sometimes the internal pull ups can be a bit inadequate. I
base this statement mostly on the published material that I've read. I never use internal pull ups.

[skimask]

well this is just an idea of the schematic, i have to add transistors to drive led display and for buzzer and 5w led

Ya know, a cheap, surplus 8x2 LCD from ebay (or something) would probably cost the same as the 7 segment LCD, less wiring to set up, a LOT easier to code, and you can get them in a relatively decent size (as in big and easy to see) and backlit. Plus, you'd have extra character space to put more characters on there, and with the extra pins not used up by the 7 segment display, you could add more features in the future. Not to mention not having to add the extra transistors+bias resistors (or mosfets).
Just a thought...

[paul borgmeier]

Also I might add that sometimes the internal pull ups can be a bit inadequate. I
base this statement mostly on the published material that I've read. I never use internal pull ups.

interesting ... I love internal pullups and have NEVER had a problem when using them in "clean" environments (e.g., low current / battery powered). If one has a noisy environment (e.g., autos), then of course they may not be strong enough to keep the pins high, BUT neither would an equivalent 25k-100k resistor. In this latter case, the failure of the weak pullups is not the fault of the internal weak pullups but of the designer. Internal pullups work as advertised and I have never seen published material that suggest otherwise. My suggestion is to understand them, use them when they are appropriate, and skip them when they are not.

[T.Jackson]

Most of the PIC-based projects in the Silicon Chip magazine don't make usage
of internal pull ups. I've spent the last 10yrs following the magazine very, very closely. I've spent the last 5yrs contributing projects to them on a part time basis. Never tried using internal pull ups - possibly because of this fact. (By the way, I think they're much higher than 25K)

[skimask]

From a few of the datasheets, parameter D070...

PortB weak pull up current
50uA minimum - 400uA maximum @ 5v, pin @ Vss. A few of the datasheets say 250uA typical

This would suggest anywhere from 12.5K to 100K of resistance per PortB pin, with a 20K typical. A bit of a wide range. Fine for a switch matrix, I'm thinking a bit sloppy for anything else...

[mister_e]

i've said that hundreds of time on many forums... they're good for lazy prototyping and/or in a well shielded enclosure. In harsh environment, they could (and sure they will) be a real pain in the... but on the flip side, it may work good... and maybe long enough to cover the warranty time

i NEVER use pull-up, never use the 'Set your pin as output and let'em floating in the air' The theory is hum hum good, but... will your design will always be powered? What happen with those pull-up when you remove the power... they're software enable after all!

[Archangel]

will your design will always be powered? What happen with those pull-up when you remove the power... they're software enable after all!

That's an excellent point, I never thought of.
JS

[precision]

i've said that hundreds of time on many forums... they're good for lazy prototyping and/or in a well shielded enclosure. In harsh environment, they could (and sure they will) be a real pain in the... but on the flip side, it may work good... and maybe long enough to cover the warranty time

i NEVER use pull-up, never use the 'Set your pin as output and let'em floating in the air' The theory is hum hum good, but... will your design will always be powered? What happen with those pull-up when you remove the power... they're software enable after all!

Please explain what is the problem in pullup, if chip have pullup feature ?
i ever useing OUTPUT PORTB.0 , is this wrong way ? Please tell what we must...


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