Post by thread:[OT]: Blinking LED softly....

John Pearson wrote: > > How can I soften the blinking of an LED so that it doesn't go on and off so abruptly? Is there a way of doing this with just an RC and no transistor? > > I am blinking an LED with a pic port and I can use either high or low to light LED. > > Thanks > > John Use Pulse Width Modulation as it comes on and goes off. Coming on, start with a narrow pulse and gradually widen it until it is fully on. Going off, gradually narrow the pulse until it is completely off. -- Best regards Tony mICros http://www.bubblesoftonline.com .....salesKILLspam@spam@bubblesoftonline.com -- http://www.piclist.com hint: To leave the PICList piclist-unsubscribe-requestKILLspammitvma.mit.edu

John Pearson <EraseMEPICLISTspam_OUTTakeThisOuTmitvma.mit.edu> wrote: > Dang, I knew I left out a very important parameter: My pic clock speed > is 240Hz. I don't think this has a software solution. John: You could try it anyway. 25% and 75% might look awful, but 33, 50, and 66 could be ok... BSF LED ;25% duty-cycle for 8/60 second. BCF LED ; GOTO $+1 ; BSF LED ; BCF LED ; GOTO $+1 ; BSF LED ;33% duty-cycle for 9/60 second. BCF LED ; NOP ; BSF LED ; BCF LED ; NOP ; BSF LED ; BCF LED ; NOP ; BSF LED ;50% duty-cycle for 8/60 second. BCF LED ; BSF LED ; BCF LED ; BSF LED ; BCF LED ; BSF LED ; BCF LED ; BSF LED ;66% duty-cycle for 9/60 second. NOP ; BCF LED ; BSF LED ; NOP ; BCF LED ; BSF LED ; NOP ; BCF LED ; BSF LED ;75% duty-cycle for 8/60 second. GOTO $+1 ; BCF LED ; BSF LED ; GOTO $+1 ; BCF LED ; BSF LED ;ON. -Andy === Andrew Warren --- aiwspam_OUTcypress.com === IPD Systems Engineering, CYSD === Cypress Semiconductor Corporation === === Opinions expressed above do not === necessarily represent those of === Cypress Semiconductor Corporation -- http://www.piclist.com hint: To leave the PICList @spam@piclist-unsubscribe-requestKILLspammitvma.mit.edu

At 06:29 PM 6/5/01 -0700, you wrote: >Dang, I knew I left out a very important parameter: My pic clock speed is >240Hz. I don't think this has a software solution. You could probably inline a handful of instructions that would give you the appearance of a soft on/off. If you assume 0.25 second is soft enough, that gives you 15 instructions, with a granularity of 16.7msec. Something like: bsf PORTA,0 bcf PORTA,0 nop nop nop bsf PORTA,0 bcf PORTA,0 bsf PORTA,0 bcf PORTA,0 bsf PORTA,0 nop nop bcf PORTA,0 bsf PORTA,0 You may have to fiddle with this a bit to get the appearance to be acceptable. Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" KILLspamspeffKILLspaminterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

On Tue, 5 Jun 2001, John Pearson wrote: > How can I soften the blinking of an LED so that it doesn't go on and > off so abruptly? Is there a way of doing this with just an RC and no > transistor? > > I am blinking an LED with a pic port and I can use either high or low > to light LED. Are you driving the LED directly from the PIC pin with a resistor? How about a cap in parallel with the LED, with a current limiting resistor between Vdd and the LED? I haven't tried this, may or may not work. Dale -- A train stops at a train station. A bus stops at a bus station. On my desk I have a workstation... -- http://www.piclist.com hint: To leave the PICList spamBeGonepiclist-unsubscribe-requestspamBeGonemitvma.mit.edu

At 09:22 PM 6/5/01 -0500, you wrote: > >Are you driving the LED directly from the PIC pin with a resistor? How >about a cap in parallel with the LED, with a current limiting resistor >between Vdd and the LED? I haven't tried this, may or may not work. It would work better with a "T" network (2 series resistors, parallel capacitor), and even better with an additional R across the LED, but the basic problem with this approach is that the capacitor gets beefy pretty fast. *IF* you use a super-bright LED at around 1mA-2mA it might be ok with something like a 220uF capacitor, depending on what he means by 'soft'. At higher currents, it's cheaper and better to just put an emitter- follower in there (series resistor) and an R-C to the base. I don't see why a little BJT would be objectionable. But software would be even better. Best regards, =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= Spehro Pefhany --"it's the network..." "The Journey is the reward" TakeThisOuTspeffEraseMEspam_OUTinterlog.com Info for manufacturers: http://www.trexon.com Embedded software/hardware/analog Info for designers: http://www.speff.com Contributions invited->The AVR-gcc FAQ is at: http://www.bluecollarlinux.com =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTmitvma.mit.edu

John Pearson wrote: > > Dang, I knew I left out a very important parameter: My pic clock speed is > 240Hz. I don't think this has a software solution. What about something like this... Sub_On movlw 10h Loop Led_On call _On Led_Off call _Off addlw 0xFF btfss STATUS,C return goto Loop _On addwf PCL nop clrw nop nop nop nop nop nop nop nop nop nop nop nop nop nop return _Off subwf PCL return -- Best regards Tony mICros http://www.bubblesoftonline.com salesEraseME.....bubblesoftonline.com -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

John Pearson wrote: > > How can I soften the blinking of an LED so that it doesn't go on and off so abruptly? Is there a way of doing this with just an RC and no transistor? > > I am blinking an LED with a pic port and I can use either high or low to light LED. Hi John, just try putting a big cap like 330uf to 1000uF range across the led. With most normal series resistors and flash speeds this will work fine. Using PWM is a bit of overkill and you won't gain any efficiency anyway. (if it's battery operated). Another option is to use a smaller cap and maybe 2 PIC pins, one is the ramp up/down pin with a larger resistor (slower ramp) and the other pin has a small resistor for full brightness in the middle. Just an idea. :o) -Roman -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

On Tue, 5 Jun 2001 22:55:31 -0400 Spehro Pefhany <EraseMEspeffINTERLOG.COM> writes: {Quote hidden}> At 09:22 PM 6/5/01 -0500, you wrote: > > > > >Are you driving the LED directly from the PIC pin with a resistor? > How > >about a cap in parallel with the LED, with a current limiting > resistor > >between Vdd and the LED? I haven't tried this, may or may not > work. > > It would work better with a "T" network (2 series resistors, > parallel > capacitor), and even better with an additional R across the LED, but > the basic problem with this approach is that the > capacitor gets beefy pretty fast. *IF* you use a super-bright LED at > around 1mA-2mA it might be ok with something like a 220uF capacitor, > depending on what he means by 'soft'. > > At higher currents, it's cheaper and better to just put an emitter- > follower in there (series resistor) and an R-C to the base. I don't > see why a little BJT would be objectionable. A cheap FET would be better in that you could use a larger resistor and smaller capacitor. I'd use an N channel FET, source to ground, drain to LED with current limit resistor. PIC drives base thru resistor. If the resistor is big enough, you may be able to rely on miller effect capacitor multiplication of the gate-drain capacity. If not, a capacitor between the gate and drain will have it's value multiplied by the gain of the circuit over what you'd get with the capacitor going to ground, again allowing an even smaller capacitor. However, as below, software is better, but here's a hardware solution with small parts. Harold > > But software would be even better. > > Best regards, > > =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -=-= > Spehro Pefhany --"it's the network..." "The Journey is > the reward" > RemoveMEspeffEraseMEEraseMEinterlog.com Info for manufacturers: > http://www.trexon.com > Embedded software/hardware/analog Info for designers: > http://www.speff.com > Contributions invited->The AVR-gcc FAQ is at: > http://www.bluecollarlinux.com > =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= -=-= > > -- > http://www.piclist.com hint: To leave the PICList > RemoveMEpiclist-unsubscribe-requestspam_OUTKILLspammitvma.mit.edu > > FCC Rules Online at http://hallikainen.com/FccRules Lighting control for theatre and television at http://www.dovesystems.com ________________________________________________________________ GET INTERNET ACCESS FROM JUNO! Juno offers FREE or PREMIUM Internet access for less! Join Juno today! For your FREE software, visit: dl.http://www.juno.com/get/tagj. -- http://www.piclist.com hint: PICList Posts must start with ONE topic: [PIC]:,[SX]:,[AVR]: ->uP ONLY! [EE]:,[OT]: ->Other [BUY]:,[AD]: ->Ads

use PWM instead of turning on and off just change the duty cycle. Andre How can I soften the blinking of an LED so that it doesn't go on and off so abruptly? Is there a way of doing this with just an RC and no transistor? I am blinking an LED with a pic port and I can use either high or low to light LED. Thanks John -- http://www.piclist.com hint: To leave the PICList RemoveMEpiclist-unsubscribe-requestTakeThisOuTspammitvma.mit.edu -- http://www.piclist.com hint: The list server can filter out subtopics (like ads or off topics) for you. See http://www.piclist.com/#topics

I did something like this for a magic trick I helped a local guy with a dinner theater develop. The LED's were controlled by two nested loops. The inner loop controlled the duty cycle and the outerloop controlled the duty % rate via a lookup table (the LED's I used had a percieved brightness rate that wasen't exaclty linear; more logrithmic, so I plotted a curve in a lookup table). --A third loop could get the thing to blink; in my application it was sufficient to bloom on and fade off. Sorry, I don't have the code handy, it was a few years ago, but you should be able to hack something pretty quick. -Dal {Original Message removed}