noob with an idea???

[seveprim]

Warnings: Moving to AVR is a one way street. Very few would turn back to PICs again after the experience.

But the AVR streets are paved with gold why would one turn to the cobble stones of a PIC!!!

 

[charlie_r]

from what i've seen so far, each has it's place.

 

[seveprim]

But that's only FOUR times, you were suggesting pulsing the LED's (and the drivers) at fifty times the current.

Never did I state 50 times the current you assumed that. You can quiet happily pulse them at high rates of current (I have found about 4 times the rated current) at high speed and not notice any real difference in brightness (dont forgret the human eye will think it is still on and if its bright enough over stimulate it (look at bright light the light it stays on well after you look away well your eyes tells your brain there is still light there) so it is all about what the human eye can detect. Dont beleive me try it for yourself

50 leds and resistor and a MCU of your choice go kill a few hours.

So in breif any led pulsed at resonable speed and 4 times it DC max current will look very bright(close to full brightness) and you would never be able to tell so you only need 4 times the current which is then averaged over x leds per second !!!

My Indcators run at 12-30volts 60milliamps (DC average)taken directly from power source they can be seen over 20 ft away (daylight) and drive total of 70 leds ) Note 20 milliamps is consumed by the micro so the leds average is about 40milliamp.

 

[Nigel Goodwin]

Never did I state 50 times the current you assumed that. You can quiet happily pulse them at high rates of current (I have found about 4 times the rated current) at high speed and not notice any real difference in brightness (dont forgret the human eye will think it is still on and if its bright enough over stimulate it (look at bright light the light it stays on well after you look away well your eyes tells your brain there is still light there) so it is all about what the human eye can detect. Dont beleive me try it for yourself

While they may be of acceptable brightness they are NOT the same brightness, and you could run individual LED's at lower power to give the same brightness level.

And from what I recall about multiplexing studies in the past, once you get to very low duty cycles you have to INCREASE the current pulses substantially to maintain a similar brightness level.

50 leds and resistor and a MCU of your choice go kill a few hours.

So in breif any led pulsed at resonable speed and 4 times it DC max current will look very bright(close to full brightness) and you would never be able to tell so you only need 4 times the current which is then averaged over x leds per second !!!

My Indcators run at 12-30volts 60milliamps (DC average)taken directly from power source they can be seen over 20 ft away (daylight) and drive total of 70 leds ) Note 20 milliamps is consumed by the micro so the leds average is about 40milliamp.

My 64 LED array is clearly visible in a bright indoors over 10m, but I've never tried it outside, nor have I bothered measuring the current taken - but they are driven solely from a PIC, no drivers.

Presumably your 70 LED's are multiplexed?, and not 1x70, so it doesn't really prove anything about your silly 1x50 suggestion?.

 

[seveprim]

While they may be of acceptable brightness they are NOT the same brightness, and you could run individual LED's at lower power to give the same brightness level.

And from what I recall about multiplexing studies in the past, once you get to very low duty cycles you have to INCREASE the current pulses substantially to maintain a similar brightness level.



My 64 LED array is clearly visible in a bright indoors over 10m, but I've never tried it outside, nor have I bothered measuring the current taken - but they are driven solely from a PIC, no drivers.

Presumably your 70 LED's are multiplexed?, and not 1x70, so it doesn't really prove anything about your silly 1x50 suggestion?.

Yes I do multiplex them .. this is getting a little rediculus the tic for tac... I am not trying to defend single pin per led nor 1 resistor for 50 leds just informing ppl you can get away with it however it is not the ideal solution nor is there any set rule to say this is how it must be done... at the end of the day if ya see the LED light up and ya happy and it dont blow up then it is correct !!!

 

[Nigel Goodwin]

I am not trying to defend single pin per led nor 1 resistor for 50 leds just informing ppl you can get away with it however it is not the ideal solution

My point through out has been that it was a completely silly suggestion, it's not practical, and only a complete idiot would 'use' such a scheme.

Bear in mind these threads and posts are permanent, posting such a useless idea could well make some beginner think it's a practical suggestion! - when (as you appear to agree?) it's completely non-practical.

 

[charlie_r]

Guys-

I didn't mean to open a can of worms here!

I would be perfectly satisfied with 1 LED driver per output, or mutiplexed.

attached is what I think will work for me.

I haven't looked at the datasheet for this particular pic, I just grabbed an 8 pin at random. I could just as easily grabbed an ATtiny for this example. I purposely didn't complete the diagram, and won't until I check the datasheets on a few.

What I need to know is if I'm on the right track or not.

 

[Nigel Goodwin]

That's fine, depending what you want to do - however, it's usually far better to have the LED's fed from the collector of the transistor (much less loss), with resistors feeding the bases.

But is five outputs all you're wanting?.

 

[charlie_r]

That was just an example of what I want. I will probably do more. I am thinking of a relatively long light bar with 15 of those 4 LED sections, and program the pic with two inputs, one for left turn and one for right, controlled by an SPDT switch. Will have to put a "debounce" circuit on each input, might use 555 monostable for that. Unless I can figure out how to use a logic gate for that.

 

[Nigel Goodwin]

That was just an example of what I want. I will probably do more. I am thinking of a relatively long light bar with 15 of those 4 LED sections, and program the pic with two inputs, one for left turn and one for right, controlled by an SPDT switch. Will have to put a "debounce" circuit on each input, might use 555 monostable for that. Unless I can figure out how to use a logic gate for that.

The whole point of micro-controllers is to make your design simple, cheap, and far more effective. You don't need to add extra devices to de-bounce switches, you do it in the software. To reduce I/O requirements, for 15 LED's multiplexing would probably be a good idea - details for 64 LED's are in my PIC tutorials.

 

[charlie_r]

Guess I haven't read far enough in your tutorials yet.....oops!

Will do a LOT more reading before ordering any parts, and see what changes as I learn more.

Thanks!

 

[Souper man]

go here and buy the uPICFAT. I have it and it works AWESOME! All you need is to connect a ICD2 (I suggest microchips ICD2) into the 6pin telephone connector and hook it up. Works like a beauty. Very well made and comes with a LCD screen, 3 buttons, reset button, adapter/power supply, 9pin extension cord, tons of I/0 pins, uses the new and better 18F452, and has expansion space beyond belief. Includes space for a usb experimenting board. I highly suggest it, as it is your safest option. As for software, I would then download MPLAB from microchip, and then download the 18F complier software. all that you can find under Microchips website. Links are below. Please follow my list of instructions and get the following:

uPICFAT ----->www.crosstheroadelectronics.com [Then contact him via email about pricing and stuff]

MPLAB ----->**broken link removed**

C18 Student Compiler ----->**broken link removed**

MPLAB ICD2 ----->**broken link removed**

A good C programming book -----> local book store, look around for a really good one!

NOTE: The uPICFAT is a development board, meaning it has all the stuff you would need for your microcontroller (power supply, crystal, etc). All you need now is to connect the I/0 pins to a breadboard and have fun! You can leave the chip in without risking bent pins. Please buy it, its worth it!

 

[blueroomelectronics]

Wow Souper man you've gone from never used a micro before to giving advice on devopment systems in about a week. Got any source code to share?

 

[Souper man]

Well, Ive been using code from him. He preprogrammed it into the "chip". Please visit www.crosstheroadelectronics.com. its a new site, but I met him in person and he helped me out so much. Please go there for good stuff.

Lol even says comes with software on it.

 

[ezuk]

Choice of a micro-controller is mainly a personal choice, but the PIC is by FAR the most popular, and generally considered the easier to learn (and also has plenty of 'grunt'). But either will easily do the job, as will almost any other micro-controller - and 'grunt' is rarely a concern, mostly they are vastly overpowered for what they do.

I do concur. I think that for a beginner, the learning curve is more important. I personally lean more towards BASIC-based solutions like the one from Tibbo or even Rabbit (although I have no experience with the latter).

The thing is that they're just easier to get a grip on. Debug right on the PC, no ladder diagrams etc... Just simple to code and work with.