Post by thread:[PIC] Best Pic for the job

James wrote : > New to the whole pic thing. Got them blinking though. > Here is my question what is the best pic chip for the job. > > 1. Lowest power consumption pic Probably one of the "nanoWatt" models. Available in both the PIC16 and PIC18 lines. > 2. Run 6 to 12 Leds A DIP16 or DIP18. 16F684/688/818/819 maybe ? > 3. Work on battery's - Like 4 double AA's Add a low power low dropout regulator. 5V or lower. > 4. Can run some sort of clock program that is user > programmable to turn off and on at certain times. Are "times" real 24h clock ("wall clock") times ? Or just "each 10 min" or something ? Will it have some interface to set time and to enter timestamps ? Keyboard ? Serial (from a PC) link ? Add a 32k crystal to tmr1 and let the PIC sleep most of the times. While awake, run on intosc for fastest startup from sleep/lowest power. > - Still trying to master the code on this > one, also I will take interface Ideas on this one. Could it > be possible to use jumper settings for this? What should the jumpers configure ? What is "this" ? Best Regards, Jan-Erik.

Well, for low power consuption, you might want to try some of the new nanowatt PICs. I think the 16F87 and the 18F1320 both have this. To run 6 to 12 LEDS, you will need 6 to 12 IO pins. Also, you will probably want a few more inputs and outputs for buttons, or jumpers. Most of the PICs with more than 18 pins should cover this. As for using jumpers for configuration, You would need some sort of system to connect the pin to either ground or 5V, depending on the jumper status. I'm not sure if the pin reads high or low when just disconnected. I think nearly all of the PICs should cover all these requirements, except the tiny 8 pin devices, and probably not the 18 pins (unless you use strobing). On 5/26/05, James <spam_OUTgogomagicTakeThisOuTcomcast.net> wrote: {Quote hidden}> > New to the whole pic thing. Got them blinking though. Here is my > question what is the best pic chip for the job. > > 1. Lowest power consumption pic > 2. Run 6 to 12 Leds > 3. Work on battery's - Like 4 double AA's > 4. Can run some sort of clock program that is user programmable to turn > off and on at certain times. - Still trying to master the code on this > one, also I will take interface Ideas on this one. Could it be possible > to use jumper settings for this? > > Thanks for the input - a humble new guy. > > James > > -

> New to the whole pic thing. Got them blinking though. Here is my > question what is the best pic chip for the job. > 1. Lowest power consumption pic The nanowatt series are supposed to use low power.. They come with internal oscillators too... Also, look for the low power parts instead of the standard parts.. > 2. Run 6 to 12 Leds Any 18pin PIC has enough I/O lines to control 12 LEDs... > 3. Work on battery's - Like 4 double AA's Yeah, they can definitely work on batteries... and if you use the low power parts, you may not even need 4x.. > 4. Can run some sort of clock program that is user programmable to turn > off and on at certain times. - Still trying to master the code on this > one, also I will take interface Ideas on this one. Could it be possible > to use jumper settings for this? Well... you could use the EEPROM to store user settings... You could use a 7seg display or LCD for the output.. but I'm not too sure what the jumpers would be for... You could use pushbuttons and build a simple menu system... Sounds a bit ambitious for a starter project though.. You might want to build it bit by bit and learn things one at a time.. Good luck!!! cheers.. -- with metta, Shawn Tan

Dave Turner wrote : > To run 6 to 12 LEDS, you will need 6 to 12 IO pins. Also, you will > probably want a few more inputs and outputs for buttons, or jumpers. > Most of the PICs with more than 18 pins should cover this. As it was specifed, 18 would do. > As for using jumpers for configuration, You would need some sort of > system to connect the pin to either ground or 5V, depending on the > jumper status. I'm not sure if the pin reads high or low when just > disconnected. Internal pullup and jumpers to gnd. With some clever technices you can get three "levels" on each pin (high/low/open), or more using external resistor networks. > I think nearly all of the PICs should cover all these requirements, > except the tiny 8 pin devices, and probably not the 18 pins (unless > you use strobing). Again, there wasn't enough in the "specs" to exclude 18-pins. Jan-Erik.

> 1. Lowest power consumption pic > 2. Run 6 to 12 Leds > 3. Work on battery's - Like 4 double AA's > 4. Can run some sort of clock program that is user programmable to turn > off and on at certain times. - Still trying to master the code on this > one, also I will take interface Ideas on this one. Could it be possible > to use jumper settings for this? > Thanks for the input - a humble new guy. If you are running a clock, then you need to run all the time, or have a pic that can take a second crystal for realtime clock at 32.768 KHz. Your real power consumption, especially if you run the LEDs even occasionally, is not going to be affected much by your choice of PIC. How about 2 or 3 AA batteries? Then you will not need a regulator(save current that way too). Since you are a beginner, do it as simply as possible, which means no multiplexing of pins. Get a 40 pin PIC like the 16F877(A) or 18F452. Cheers, Bob

----- Original Message ----- From: "Dave Turner" <.....dave.w.turnerKILLspam@spam@gmail.com> Subject: Re: [PIC] Best Pic for the job > Well, for low power consuption, you might want to try some of the new > nanowatt PICs. I think the 16F87 and the 18F1320 both have this. The 16LF87/88 will run down to 2 volts, so a 3 volt lithium cell could be comfortable. They have an onboard oscillator freeing up two more pins as I/O, and the oscillator is programmable so you can manage the power consumption even further. > I think nearly all of the PICs should cover all these requirements, > except the tiny 8 pin devices, and probably not the 18 pins (unless > you use strobing). He is only talking 6-12 LEDs plus a button or two. An 18 pin part with an onboard oscillator is going to have 15 or 16 pins available, depending on whether you reuse !MCLR. If you want to do ICSP and have obnoxious circuitry on all pins you might get down to 13 I/O. With two buttons, that's still 11 LEDs. If you insist on a crystal you are down to 9 LEDs, and that's worst case, still in the 6-12 range. --McD

On Thu, May 26, 2005 at 01:57:45PM -0600, James wrote: > > New to the whole pic thing. Cool. > Got them blinking though. Excellent. > Here is my question what is the best pic chip for the job. Fire away. > > 1. Lowest power consumption pic > 3. Work on battery's - Like 4 double AA's These two go together. > 2. Run 6 to 12 Leds This is incompatible with the first two goals. Unless you are doing intermittent blinking LEDs, the LEDs will consume several of orders of magnitude more of your battery power than the PIC ever will. BTW any PIC with 18 or more pins should be able to handle that job. > 4. Can run some sort of clock program that is user programmable to turn > off and on at certain times. - Still trying to master the code on this > one, also I will take interface Ideas on this one. Could it be possible > to use jumper settings for this? Of course. But as a first crack I would suggest doing a 3 button up/down/select interface. Then you only need to read (and debounce) three buttons to get the interface. Also you'll find clocks tougher than you think. Any timer that's not temperature compensated will drift. So they'll get out of time pretty quick. I have a rather complex sunrise/sunset outdoor light controller that has many of the functions you require. No schematic (sorry!) but the code can be found here: http://www.finitesite.com/d3jsys/clock.asm You will find code for managing an LCD display, tracking a time for a clock/calendar, and other goodies. Hope it helps, BAJ

On Thu, May 26, 2005 at 02:30:33PM -0700, phil B wrote: > There are lots of techniques for multiplexing pins to > get more than 1 LED per pin. Numerous microchip app > and design notes on this topic. Look at how 7 seg > displays are done to get an idea (you may not need > drive transistors). There was also a microchip > newsletter (iirc) article from about a year ago that > got a goodly number of LEDs per pin by using output L, > H and high Z (input) plus a bit of mental gymnastics. > > > My favorite answer is a 12F509 + 2 74HC595s (to drive > up to 16 LEDs) but I suspect thats not what is being > looked for. Phil, It begs an interesting question. Why is that combo better than a 28 or 40 pin PIC? BAJ

Bob, For low battery application 18LF452 is better. Andre -----Original Message----- From: EraseMEpiclist-bouncesspam_OUTTakeThisOuTmit.edu [piclist-bouncesspam_OUTmit.edu] On Behalf Of Bob Blick Sent: Thursday, May 26, 2005 1:38 PM To: Microcontroller discussion list - Public. Subject: Re: [PIC] Best Pic for the job > 1. Lowest power consumption pic > 2. Run 6 to 12 Leds > 3. Work on battery's - Like 4 double AA's > 4. Can run some sort of clock program that is user programmable to turn > off and on at certain times. - Still trying to master the code on this > one, also I will take interface Ideas on this one. Could it be possible > to use jumper settings for this? > Thanks for the input - a humble new guy. If you are running a clock, then you need to run all the time, or have a pic that can take a second crystal for realtime clock at 32.768 KHz. Your real power consumption, especially if you run the LEDs even occasionally, is not going to be affected much by your choice of PIC. How about 2 or 3 AA batteries? Then you will not need a regulator(save current that way too). Since you are a beginner, do it as simply as possible, which means no multiplexing of pins. Get a 40 pin PIC like the 16F877(A) or 18F452. Cheers, Bob

part 1 1971 bytes content-type:text/plain; charset="us-ascii"; format=flowedAt 03:47 PM 5/26/2005, Byron A Jeff wrote: > > > > My favorite answer is a 12F509 + 2 74HC595s (to drive > > up to 16 LEDs) but I suspect thats not what is being > > looked for. > >It begs an interesting question. Why is that combo better than >a 28 or 40 pin PIC? I love questions like this <grin>. Why indeed? My usual responses: 1) I can use a smaller packaged PIC (6 or 8 pins if the only thing is to read a few switches and drive LEDs). 2) I can place the LED drivers near the LEDs and connect with only 2 or 3 lines plus power and ground. Handy if the PIC is located elsewhere. 3) I can drive the LEDs from an un-regulated supply and keep the PIC supply nice and clean. (this is a trick answer: unreg supply is about anywhere from 3.3 to 6V if using 74hc595 or just about anything at all if using TPIC6595) 3b) Can drive reasonable sized relays instead of LEDs if using TPIC6595. 4) 74hc595 are just SOooo darned inexpensive! Drive 8 LEDs for 10 cents or so. 5) One of my boards has 40 status LEDs on it as well as 3- 7 segment displays. Also has 16 or so digital inputs (both binary and trinary). All driven with only 3 i/o lines from PIC. No question: if this is a one-off hobbyist project that needs only 12 LEDs, spend the extra dollars and go for a larger PIC. But **I** would probably do it with a tiny PIC and shift registers simply because that's what I'm used to doing for larger projects. And I just happen to have several hundred (or more) little (1" x 3") single-sided PCBs that hold an 8 pin PIC, simple 5V zener PSU (with JFET discharge circuit), 2- trimpots wired for RC time measurements, 3- digital inputs, 2- TPIC6595 shift registers. The PIC section can be snipped off, leaving the remainder of the board with the 2- shift registers to connected to previous boards to make a SR chain as long as needed. They get used for all kinds of simple projects. dwayne part 2 7298 bytes content-type:image/gif; name="L342A2-01.GIF"; (decode) part 3 519 bytes content-type:text/plain; charset="us-ascii"; format=flowed -- Dwayne Reid <@spam@dwaynerKILLspamplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 21 years of Engineering Innovation (1984 - 2005) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email. part 4 35 bytes content-type:text/plain; charset="us-ascii" (decoded 7bit)

You beat me to it! Well put. I would also add that the 595s allow you add more LEDs (or what ever) in units of 8 by chaining them. No real gymnastics needed, just pump the bits out via bit bang SPI (which is only slightly more complex than bsf/bcf). There is a practical limit but its pretty high. I used them on an LED light stick design - I've had as high as 128 working. The bike light project in the current Nuts and Volts could have benefitted from this approach. Another issue is board space. A 40 pin PIC takes up a lot more space than an 8 or 14 pin one. A 40 pin PIC seems like over kill to light up 32 LEDs. Phil --- Dwayne Reid <KILLspamdwaynerKILLspamplanet.eon.net> wrote: {Quote hidden}> At 03:47 PM 5/26/2005, Byron A Jeff wrote: > > > > > > My favorite answer is a 12F509 + 2 74HC595s (to > drive > > > up to 16 LEDs) but I suspect thats not what is > being > > > looked for. > > > >It begs an interesting question. Why is that combo > better than > >a 28 or 40 pin PIC? > > I love questions like this <grin>. Why indeed? > > My usual responses: > > 1) I can use a smaller packaged PIC (6 or 8 pins if > the only thing is to > read a few switches and drive LEDs). > > 2) I can place the LED drivers near the LEDs and > connect with only 2 or 3 > lines plus power and ground. Handy if the PIC is > located elsewhere. > > 3) I can drive the LEDs from an un-regulated supply > and keep the PIC supply > nice and clean. (this is a trick answer: unreg > supply is about anywhere > from 3.3 to 6V if using 74hc595 or just about > anything at all if using > TPIC6595) > > 3b) Can drive reasonable sized relays instead of > LEDs if using TPIC6595. > > 4) 74hc595 are just SOooo darned inexpensive! Drive > 8 LEDs for 10 cents or so. > > 5) One of my boards has 40 status LEDs on it as well > as 3- 7 segment > displays. Also has 16 or so digital inputs (both > binary and trinary). All > driven with only 3 i/o lines from PIC. > > > No question: if this is a one-off hobbyist project > that needs only 12 LEDs, > spend the extra dollars and go for a larger PIC. > > But **I** would probably do it with a tiny PIC and > shift registers simply > because that's what I'm used to doing for larger > projects. And I just > happen to have several hundred (or more) little (1" > x 3") single-sided PCBs > that hold an 8 pin PIC, simple 5V zener PSU (with > JFET discharge circuit), > 2- trimpots wired for RC time measurements, 3- > digital inputs, 2- TPIC6595 > shift registers. The PIC section can be snipped > off, leaving the remainder > of the board with the 2- shift registers to > connected to previous boards to > make a SR chain as long as needed. They get used > for all kinds of simple > projects. > > dwayne > > -- > Dwayne Reid <RemoveMEdwaynerTakeThisOuTplanet.eon.net> > Trinity Electronics Systems Ltd Edmonton, AB, > CANADA > (780) 489-3199 voice (780) 487-6397 fax > > Celebrating 21 years of Engineering Innovation (1984 > - 2005) > .-. .-. .-. .-. .-. .-. .-. .-. > .-. .- > `-' `-' `-' `-' `-' `-' `-' `-' > `-' > Do NOT send unsolicited commercial email to this > email address. > This message neither grants consent to receive > unsolicited > commercial email nor is intended to solicit > commercial email. > > --

On 5/26/05, James <spamBeGonegogomagicspamBeGonecomcast.net> wrote: > > New to the whole pic thing. Got them blinking though. Here is my > question what is the best pic chip for the job. > > 1. Lowest power consumption pic > 2. Run 6 to 12 Leds PIC16F630 or PIC16F676 6 pin PIC is more than enough for running 12 LED, without additional hardware. Application with 16F628: http://surducan.netfirms.com/conexclub/main.html Vasile > 3. Work on battery's - Like 4 double AA's > 4. Can run some sort of clock program that is user programmable to turn > off and on at certain times. - Still trying to master the code on this > one, also I will take interface Ideas on this one. Could it be possible > to use jumper settings for this? > > Thanks for the input - a humble new guy. > > James > > -

The Fairchild 74HC595 datasheet specs a max current of 35mA per pin though I wouldn't get anywhere near that with out a pretty gentle duty cycle. The dip package has a 600 mW limit, and the SO's is 500 mW. I've run a number of tests on it because I was concerned. With all 8 outputs constantly driving LEDS at 10 mA for 24 hrs there was very little heat increase (a couple degrees F) so the 500 mW limit may be conservative. This was with both Fairchild and ST parts. Any kind of <100% duty cycle is going to help here as well. One thing to be carefull of is inrush current and spikes on the clock and serial in pin. I use a 1K limiter and 100K to ground on both RCLK and SERIN. Phil --- PicDude <TakeThisOuTpicdude2EraseMEspam_OUTnarwani.org> wrote: {Quote hidden}> On Thursday 26 May 2005 04:30 pm, phil B scribbled: > > My favorite answer is a 12F509 + 2 74HC595s (to > drive > > up to 16 LEDs) but I suspect thats not what is > being > > looked for. > > > > Phil > > > Doesn't the 74HC595 not have the current output > capability of a PIC? IIRC it > was something like 5-6mA for the 74HC595, which IMO > is not much for driving > LED's properly. But of course, it depends on the > specific LEDs and > application of the OP. > > Cheers, > -Neil. > > > --

I just checked the TI & Fairchild datasheets -- interesting that you work with the "absolute maximum rating" of 35mA. Though the Fairchild does not specifically state a normal high and low output current, the TI datasheet specs this as "+/- 6mA output drive", but also states an absolute max of 35mA. I asking this because it's piqued my interest for future use. I usually have a self-coded PWM routine to allow dimming of the LEDs from 1/9 to 9/9 duty-cycle, and on a newer experiment, I'm trying to see if I can easily dim different LEDs to different intensities. If I can swing the current I need when at 100% duty cycle, I'm trying to think of how intense the data output (from the PIC to the shift register) could be to do software dimming. I also see it has an output-enable pin, which could be used for global dimming (at the cost of 1 extra pin), but not for multiple-level dimming. I'll have to think about this some more... Cheers, -Neil. On Friday 27 May 2005 01:54 am, phil B scribbled: {Quote hidden}> The Fairchild 74HC595 datasheet specs a max current of > 35mA per pin though I wouldn't get anywhere near that > with out a pretty gentle duty cycle. The dip package > has a 600 mW limit, and the SO's is 500 mW. > > I've run a number of tests on it because I was > concerned. With all 8 outputs constantly driving LEDS > at 10 mA for 24 hrs there was very little heat > increase (a couple degrees F) so the 500 mW limit may > be conservative. This was with both Fairchild and ST > parts. Any kind of <100% duty cycle is going to help > here as well. > > One thing to be carefull of is inrush current and > spikes on the clock and serial in pin. I use a 1K > limiter and 100K to ground on both RCLK and SERIN. > > Phil > > --- PicDude <RemoveMEpicdude2TakeThisOuTnarwani.org> wrote: > > On Thursday 26 May 2005 04:30 pm, phil B scribbled: > > > My favorite answer is a 12F509 + 2 74HC595s (to > > > > drive > > > > > up to 16 LEDs) but I suspect thats not what is > > > > being > > > > > looked for. > > > > > > Phil > > > > Doesn't the 74HC595 not have the current output > > capability of a PIC? IIRC it > > was something like 5-6mA for the 74HC595, which IMO > > is not much for driving > > LED's properly. But of course, it depends on the > > specific LEDs and > > application of the OP. > > > > Cheers, > > -Neil. > > > > > > --

>> The OPs 'low-power' requirements are in significant conflict with >> illuminating 6 to 12 LEDs. > >That was my first observation. The only way it could have been worse >is specifying a 9V battery for the power source. <VBG> so the OP could add some switching regulator experience as well - but then I am not sure if a 9V battery has a better watts/cubic cm than AA cells. >One aside on my other post: my sunrise/sunset light controller >drifts too. I usually have to reset it at least once a month. Sounds like time to add a radio clock - or have a photo cell that detects the daylight time and sets midnight to the midpoint between sunrise and sunset each night. Don't know if that would be accurate enough - maybe in very low rainfall/cloud cover areas.

----- Original Message ----- From: "phil B" <philpiclistEraseME.....yahoo.com> To: "Microcontroller discussion list - Public." <EraseMEpiclistmit.edu> Sent: Friday, May 27, 2005 2:54 AM Subject: Re: [PIC] Best Pic for the job {Quote hidden}> The Fairchild 74HC595 datasheet specs a max current of > 35mA per pin though I wouldn't get anywhere near that > with out a pretty gentle duty cycle. The dip package > has a 600 mW limit, and the SO's is 500 mW. > > I've run a number of tests on it because I was > concerned. With all 8 outputs constantly driving LEDS > at 10 mA for 24 hrs there was very little heat > increase (a couple degrees F) so the 500 mW limit may > be conservative. This was with both Fairchild and ST > parts. Any kind of <100% duty cycle is going to help > here as well. > > One thing to be carefull of is inrush current and > spikes on the clock and serial in pin. I use a 1K > limiter and 100K to ground on both RCLK and SERIN. > > Phil At 10ma the Vol (low output voltage) of the 74HC is probably quite a bit less than 1 volt. So, assuming worst case: 1 V * 10 mA * 8 = 8mW Not much dissipation at all. Bob Ammerman RAm Systems

drive it low if its jumpered it wont matter if its unjumpered then enable wpu and check {Quote hidden}> -----Original Message----- > From: RemoveMEpiclist-bouncesEraseMEEraseMEmit.edu [RemoveMEpiclist-bouncesspam_OUTKILLspammit.edu]On Behalf > Of Chris Emerson > Sent: Friday, May 27, 2005 20:50 > To: Microcontroller discussion list - Public. > Subject: Re: [PIC] Best Pic for the job > > > On Fri, May 27, 2005 at 11:45:26AM +0100, Alan B. Pearce wrote: > > >> >Internal pullup and jumpers to gnd. > > >> > > >> However this technique does not usually result in a "low > > >> power processor because of the way the internal pullups > > >> work. > > > > > >Only turn on wpu while checking the pin ? > > > > Yeah, someone else pointed that out too. > > But then don't you have a floating input if the jumper's not in place? > That'll probably eat up more current than the weak pullup. > > Chris > --

Minor correction. 10 mA * 1V = 10 mW 8 pins makes for 80 mW. Still not enough to worry about. If you tie the LED high and light it by driving the output low don't you get the higher differential voltage (and thus the higher wattage)? I chose to tie low and drive high (no personal comments, please!). the outputs were at around 4.5 V (iirc) so it was a bit higher. I use 5 for a conservative (and easier to do in my head) number. That works out to be a bit less than 400 mW. Something that I wanted to look at but never got to was to run the 595s at a lower Vcc to get output high to be the LED voltage drop (lets say 2V for arguments sake). Then the max dissipation would be 2*8*10 (160mW) and eat less battery. You will see more voltage drop with a higher current. It wasn't too bad at 10mA as I recall. I still don't think drawing < 1/3 the max spec is abusive and my experience reinforces that. Phil --- Bob Ammerman <RemoveMErammermanTakeThisOuTspamverizon.net> wrote: > > {Original Message removed}

At 08:44 AM 5/27/2005, phil B wrote: >Something that I wanted to look at but never got to >was to run the 595s at a lower Vcc to get output high >to be the LED voltage drop (lets say 2V for arguments >sake). Then the max dissipation would be 2*8*10 >(160mW) and eat less battery. I do something similar with that 40- LED board I described earlier. All the logic runs from a simple zener-regulated 5V supply but the LEDs anodes are all connected to a Nat-Semi simple switcher set at 3.3V. The LEDs illuminate when driven LO by the hc595 and are reverse-biased with somewhat less than 2 volts while off. Well within the LED specs. This display card is mounted to a piece of Lexan fitted to a cut opening in an industrial control panel. It makes for a completely water-tight and fairly good-looking display but total dissipation was a concern. Running the LEDs at that low voltage kept the temperature rise very low. Not using a switcher would have resulted in considerable heat, given that the whole thing is running from a 24Vac supply. Note that the hc595s are running from the same 5V supply as the PIC - only the LEDs are run at 3.3V. Another advantage of doing it this way is that the mosfets in the output stages of the hc595 are fully enhanced. Running the hc595 at 3.3V results in much higher RDSon and hotter chips. dwayne -- Dwayne Reid <EraseMEdwaynerspamspamBeGoneplanet.eon.net> Trinity Electronics Systems Ltd Edmonton, AB, CANADA (780) 489-3199 voice (780) 487-6397 fax Celebrating 21 years of Engineering Innovation (1984 - 2005) .-. .-. .-. .-. .-. .-. .-. .-. .-. .- `-' `-' `-' `-' `-' `-' `-' `-' `-' Do NOT send unsolicited commercial email to this email address. This message neither grants consent to receive unsolicited commercial email nor is intended to solicit commercial email.