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Discussion Groups | Piclist | Selecting resistor values for 3 pb switches on one ADC input pin
A discussion group for the PICMicro microcontroller. Also called the Microchip PIC, this list is dedicated to the use and abuse of this fine, simple, microcontroller. Close to topic posts are welcome, ie. general electronics.
Selecting resistor values for 3 pb switches on one ADC input pin - ransom peek - Mar 4 13:13:00 2004
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Am trying to read three pushbutton switches with one ADC (16F688) input pin, using voltage divider method, and need help choosing resistor values . There is a Microchip app note showing use of comparator to read multiple switches (capacitor charge timing), but this seems more complicated from a software standpoint. R1 -------------/\/\/\/\/\-------- +3V (VCC) | | | | R2 R3 ADC I/O ----------------------/\/\/\/\/\------------------------------/\/\/\/\/\------- | | | | | | \ \ \ SW1 \ SW2 \ SW3 \ | | | | | | GND GND GND The Microchip 16F688 data sheet advises that for the ADC, the “maximum recommended impedance for analog sources is 10K ohms”. One (non – Microchip) design note recommends that the divider network slices the range into equal sized “bins”, as follows : BIN SIZE = 2 raised to the # bits in the ADC / # keys scanned. First choose pull up (R1) resistor value. Then use formula for the other resistors: 10 So BIN SIZE = 2 / 3 = 1024 / 3 = 341 ohms. Trade off, I think is lower power usage with higher resistance values, faster conversion speed for lower values. For my application, will poll the ADC to read one of three pushbuttons (not simultaneous on). Need minimum power usage, but not sure if the conversion speed makes any difference So, my best guess is to choose resistors as follows: R1 (pullup) 8.2K ohm R2 360 ohm (common value close to 341 ohms) R3 360 ohm So the three possible voltage into the ADC would be: SW1 0 volts SW2 [360/(8200+360)] * 3 volts = 0.042 volts SW3 [720/(8200+720)] * 3 volts = 0.081 volts
Is this enough differential for reliability and simplified coding? Shouldn’t I try for more differential by increasing R2 and R3, and reducing R1 to keep it all within the 10K ohm limit. Is the 10k ohm ADC impedance limitation calculated from the ADC pin to VCC (thru R1) or Ground (thru the other resistors)? I need some help! One more thing – one example I found on the internet shows this kind of design with a 1 nf (nanofarad I assume) cap between the ADC pin and ground. Other examples do not show this. Is this important? Ransom Peek |
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Re: Selecting resistor values for 3 pb switches on one ADC input pin - Chad Russel - Mar 4 19:46:00 2004
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Hint: 341 is bits, not ohms. :) Chad ===== My software has no bugs. Only undocumented features. __________________________________ |
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Re: Selecting resistor values for 3 pb switches on one ADC input pin - Chad Russel - Mar 4 21:42:00 2004
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Ok. This method will detect one of three switches, but not multiple presses. That is a little more complicated and requires 9 bins instead of 3. Easier for me to look at voltage ratios. With no switches pressed the input will be VCC and with SW1 pressed the input will be zero volts. Easy so far? Now the next trick is to evenly divide the two remaining switches. To make life easy set R1 to 10K, then the input impedance will always be less than 10K. (I can show you the math to nail that at 10K max if you want.) Next consider SW3 because that will be both resistors in series and the next highest voltage which we would like to be 2/3 * Vcc. Make R2 + R3 = RA. Then RA/(R1 + RA) = 2/3 > RA = 20K. If SW2 is pressed we want a voltage of 1/3 * Vcc > R2/(R1 + R2) = 1/3 > R2 = R1/2 > R1 = 5K. R1 + R2 = RA so R2 = 15K. Check my math. Chad --- ransom peek <> wrote: > Am trying to read three pushbutton switches with one ADC (16F688) > input > pin, using voltage divider method, and need help choosing resistor > values . There is a Microchip app note showing use of comparator to > read multiple switches (capacitor charge timing), but this seems more > complicated from a software standpoint. > R1 > -------------/\/\/\/\/\-------- +3V (VCC) > | > | > | > | R2 > R3 > ADC I/O > ----------------------/\/\/\/\/\------------------------------/\/\/\/\/\ > ------- > | | > | > | | > | > \ \ > \ > SW1 \ SW2 \ > SW3 \ > | | > | > | | > | > GND GND > GND > > The Microchip 16F688 data sheet advises that for the ADC, the > "maximum > recommended impedance for analog sources is 10K ohms". > > One (non - Microchip) design note recommends that the divider network > slices the range into equal sized "bins", as follows > : > BIN SIZE = 2 raised to the # bits in the ADC / # keys scanned. > > First choose pull up (R1) resistor value. Then use formula for > the > other resistors: > > 10 > So BIN SIZE = 2 / 3 = 1024 / 3 = 341 ohms. > > Trade off, I think is lower power usage with higher resistance > values, > faster conversion speed for lower values. For my application, will > poll > the ADC to read one of three pushbuttons (not simultaneous on). > > Need minimum power usage, but not sure if the conversion speed makes > any > difference > So, my best guess is to choose resistors as follows: > > R1 (pullup) 8.2K ohm > R2 360 ohm (common value close to 341 ohms) > R3 360 ohm > > So the three possible voltage into the ADC would be: > > SW1 0 volts > SW2 [360/(8200+360)] * 3 volts = 0.042 volts > > SW3 [720/(8200+720)] * 3 volts = 0.081 volts > > Is this enough differential for reliability and simplified coding? > Shouldn't I try for more differential by increasing R2 and R3, and > reducing R1 to keep it all within the 10K ohm limit. Is the 10k ohm > ADC > impedance limitation calculated from the ADC pin to VCC (thru R1) or > Ground (thru the other resistors)? > > I need some help! > > One more thing - one example I found on the internet shows this kind > of > design with a 1 nf (nanofarad I assume) cap between the ADC pin and > ground. Other examples do not show this. Is this important? > > Ransom Peek ===== My software has no bugs. Only undocumented features. __________________________________ |
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Re: Selecting resistor values for 3 pb switches on one ADC input pin - Dave Mucha - Mar 5 9:08:00 2004
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I'm not sure it is this complicated. Since you listed ADC as your inputs, we'll start there. The ADC is 10 bit or 1024 discrete steps, change your math if your ADC is different. Using a pair of resistors as a voltage divider will yield some value between 0 and 1024 bits. A pair if same value resistors will yield 512. This is bits input in the uC, but 2.5 volts on the input pin. If you were looking at one switch, (same sized resistors) you could look for anything above 256. That would offer a window for the pull down(up?) resistor to keep the ADC at zero, and the switch to deliver 2.5 volts or 512 bits. Having the threshold at 511 to see 512 would be a pretty poor choice as any variation in resistances would possibly alter the actual range. splitting the difference and looking to see if it is more than half way or less than half way offers a pretty large window. ie: with half voltage and half ADC input and half bits in the micro, your threshold to verify the switch was pressed would be one quarter the range, or mid point between the signal value and your non-signal value. Assume 3 switches, all equally rated, say all at 10k ohm, plus the pulldown(up?) at 10k also. Each would offer 512 when pressed, but 2 pressed at the same time would offer different numbers and 3 pressed at the same time would also yield a different number. The problem is you would not know which switch was pressed. Only that one, two or three switch were pressed. Select each switch to have a different resistance and then make sure the added values would wind up being different voltages. Then, select the mid point between those calculated values as the toggle point in software. a 1k, a 3k and a 5k will each offer a different voltage and the 1k and 3k will yield 4k. So you would have 3 distinct ranges. to keep the math simple, think 5k as the pull down, and each switch offers a different input to the ADC. IMPORTANT => ADD debounce. a cap would offer a voltage value after the switch is pressed, but voltage decay would have the voltage passing thru each voltage range. would make for some odd readings. A SECOND APPROACH Another input method would be to use an RC to generate pulses that can be read on an input pin NOT and ADC input. You can detect switches on an ADC channel or from a RC input as pulses. That changes the calculations for selection, but not overall concept. A CAP is REQUIRES as it is integral to the RC pulse generator that creates the pulses. Since it too will degrade and the value will cross other inputs, consider the time constant and use that in your debounce software. A THIRD APPROACH When using more than 3 switches, look to a serial input chip that would see 8 inputs and report via serial back to your uC the status. Those can be daisy changed for lots and lots and lots of switches. And for those, you can poll them continuously, or connect it so that any switch will alert your uC to poll because a switch was pressed. Dave ps: please feel free to comment on the best approach. |
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16f877 - peter hadge - Mar 5 23:12:00 2004
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hi all,
if i want to control 8 relays by the 16F877, could i connect these relayes directly
to 8 output from the PIC without using any kind of buffers or any other
components?
thanx
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RE: 16f877 - Carlos Marcano - Mar 5 23:43:00 2004
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You
shouldnt. Better use transistors to drive the relays.
Regards,
*Carlos*
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Re: 16f877 - Chad Russel - Mar 5 23:43:00 2004
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Depends on the relay drive requirements. Are they higher or lower than the PIC is capable of driving. Most likely higher. --- peter hadge <> wrote: > hi all, > > if i want to control 8 relays by the 16F877, could i connect these > relayes directly to 8 output from the PIC without using any kind of > buffers or any other components? > thanx > > > --------------------------------- > ===== My software has no bugs. Only undocumented features. __________________________________ |
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Re: 16f877 - Phil - Mar 6 2:21:00 2004
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Your 5V relay coils are likely to pull 80-100 mA. way too much for the PIC. check this page out. <http://ourworld.compuserve.com/homepages/Bill_Bowden/r_ctrl.htm> its a good summary of how to drive relays. If you are using 5V relays, you can use option B which doesn't require a resistor. I'm using 2n2222s to drive several 5V relays in my latest project. Dont forget the diode for each coil as it keeps the smoke in. By the way, you might also want to look at solid state relays. They are bit more expensive but dont require the clamping diode or drive transistor so its less space, a much cleaner layout and a far longer life cycle. Inexpensive relays are often only spec'd for 100K operations - cycle 100 times a day and it will last only 3 years. --- In , peter hadge <pt2263@y...> wrote: > hi all, > > if i want to control 8 relays by the 16F877, could i connect these relayes directly to 8 output from the PIC without using any kind of buffers or any other components? > thanx > > > --------------------------------- > |
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RE: Selecting resistor values for 3 pb switches on one ADC input pin - ransom peek - Mar 6 11:11:00 2004
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Thank you Chad! I will use the 10K, 5K and 20K ohms values as you advise. You advise that with the pull up resistor at 10k ohms, then the input impedance will always be less than 10k. Is the input impedance measured between I/O pin and ground or VCC? Could you kindly show how the math works for this? Ransom Peek -----Original Message----- From: Chad Russel [mailto:] Sent: Thursday, March 04, 2004 7:42 PM To: Subject: Re: [piclist] Selecting resistor values for 3 pb switches on one ADC input pin Ok. This method will detect one of three switches, but not multiple presses. That is a little more complicated and requires 9 bins instead of 3. Easier for me to look at voltage ratios. With no switches pressed the input will be VCC and with SW1 pressed the input will be zero volts. Easy so far? Now the next trick is to evenly divide the two remaining switches. To make life easy set R1 to 10K, then the input impedance will always be less than 10K. (I can show you the math to nail that at 10K max if you want.) Next consider SW3 because that will be both resistors in series and the next highest voltage which we would like to be 2/3 * Vcc. Make R2 + R3 = RA. Then RA/(R1 + RA) = 2/3 > RA = 20K. If SW2 is pressed we want a voltage of 1/3 * Vcc > R2/(R1 + R2) = 1/3 > R2 = R1/2 > R1 = 5K. R1 + R2 = RA so R2 = 15K. Check my math. Chad --- ransom peek <> wrote: > Am trying to read three pushbutton switches with one ADC (16F688) > input > pin, using voltage divider method, and need help choosing resistor > values . There is a Microchip app note showing use of comparator to > read multiple switches (capacitor charge timing), but this seems more > complicated from a software standpoint. > R1 > -------------/\/\/\/\/\-------- +3V (VCC) > | > | > | > | R2 > R3 > ADC I/O > ----------------------/\/\/\/\/\------------------------------/\/\/\/\/\ > ------- > | | > | > | | > | > \ \ > \ > SW1 \ SW2 \ > SW3 \ > | | > | > | | > | > GND GND > GND > > The Microchip 16F688 data sheet advises that for the ADC, the > "maximum > recommended impedance for analog sources is 10K ohms". > > One (non - Microchip) design note recommends that the divider network > slices the range into equal sized "bins", as follows > : > BIN SIZE = 2 raised to the # bits in the ADC / # keys scanned. > > First choose pull up (R1) resistor value. Then use formula for > the > other resistors: > > 10 > So BIN SIZE = 2 / 3 = 1024 / 3 = 341 ohms. > > Trade off, I think is lower power usage with higher resistance > values, > faster conversion speed for lower values. For my application, will > poll > the ADC to read one of three pushbuttons (not simultaneous on). > > Need minimum power usage, but not sure if the conversion speed makes > any > difference > So, my best guess is to choose resistors as follows: > > R1 (pullup) 8.2K ohm > R2 360 ohm (common value close to 341 ohms) > R3 360 ohm > > So the three possible voltage into the ADC would be: > > SW1 0 volts > SW2 [360/(8200+360)] * 3 volts = 0.042 volts > > SW3 [720/(8200+720)] * 3 volts = 0.081 volts > > Is this enough differential for reliability and simplified coding? > Shouldn't I try for more differential by increasing R2 and R3, and > reducing R1 to keep it all within the 10K ohm limit. Is the 10k ohm > ADC > impedance limitation calculated from the ADC pin to VCC (thru R1) or > Ground (thru the other resistors)? > > I need some help! > > One more thing - one example I found on the internet shows this kind > of > design with a 1 nf (nanofarad I assume) cap between the ADC pin and > ground. Other examples do not show this. Is this important? > > Ransom Peek ===== My software has no bugs. Only undocumented features. __________________________________ to unsubscribe, go to http://www.yahoogroups.com and follow the instructions Yahoo! Groups Links |
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RE: Selecting resistor values for 3 pb switches on one ADC input pin - Chad Russel - Mar 6 13:12:00 2004
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Input impedance is the resistance the input pin sees. Since VCC and ground are both zero ohms then to either or both. 10K to vcc and 10 K to ground = output impedance of 5K. Any leakage current has to flow through the output impedance. The leakage current developes a voltage which equals an error component. The lower the resistance the lower the error. The 10K maximum number is just a good rule for the +/- 1.0 ua leakage current which = +/- 10 millivolt error. Chad --- ransom peek <> wrote: > Thank you Chad! I will use the 10K, 5K and 20K ohms values as you > advise. You advise that with the pull up resistor at 10k ohms, then > the > input impedance will always be less than 10k. Is the input impedance > measured between I/O pin and ground or VCC? Could you kindly show > how > the math works for this? > > Ransom Peek > > -----Original Message----- > From: Chad Russel [mailto:] > Sent: Thursday, March 04, 2004 7:42 PM > To: > Subject: Re: [piclist] Selecting resistor values for 3 pb switches on > one ADC input pin > > Ok. This method will detect one of three switches, but not multiple > presses. That is a little more complicated and requires 9 bins > instead > of 3. > > Easier for me to look at voltage ratios. With no switches pressed > the > input will be VCC and with SW1 pressed the input will be zero volts. > Easy so far? Now the next trick is to evenly divide the two > remaining > switches. To make life easy set R1 to 10K, then the input impedance > will always be less than 10K. (I can show you the math to nail that > at > 10K max if you want.) > > Next consider SW3 because that will be both resistors in series and > the > next highest voltage which we would like to be 2/3 * Vcc. Make R2 + > R3 > = RA. Then RA/(R1 + RA) = 2/3 > RA = 20K. > > If SW2 is pressed we want a voltage of 1/3 * Vcc > R2/(R1 + R2) = 1/3 > > > R2 = R1/2 > R1 = 5K. > > R1 + R2 = RA so R2 = 15K. > > Check my math. > Chad > > --- ransom peek <> wrote: > > Am trying to read three pushbutton switches with one ADC (16F688) > > input > > pin, using voltage divider method, and need help choosing resistor > > values . There is a Microchip app note showing use of comparator > to > > read multiple switches (capacitor charge timing), but this seems > more > > complicated from a software standpoint. > > > > > > R1 > > -------------/\/\/\/\/\-------- +3V (VCC) > > | > > | > > | > > | R2 > > R3 > > ADC I/O > > > ----------------------/\/\/\/\/\------------------------------/\/\/\/\/\ > > ------- > > | | > > | > > | | > > | > > \ \ > > \ > > SW1 \ SW2 \ > > SW3 \ > > | | > > | > > | | > > | > > GND GND > > GND > > > > > > > > The Microchip 16F688 data sheet advises that for the ADC, the > > "maximum > > recommended impedance for analog sources is 10K ohms". > > > > One (non - Microchip) design note recommends that the divider > network > > slices the range into equal sized "bins", as follows > > : > > BIN SIZE = 2 raised to the # bits in the ADC / # keys scanned. > > > > First choose pull up (R1) resistor value. Then use formula for > > the > > other resistors: > > > > 10 > > So BIN SIZE = 2 / 3 = 1024 / 3 = 341 ohms. > > > > Trade off, I think is lower power usage with higher resistance > > values, > > faster conversion speed for lower values. For my application, will > > poll > > the ADC to read one of three pushbuttons (not simultaneous on). > > > > Need minimum power usage, but not sure if the conversion speed > makes > > any > > difference > > So, my best guess is to choose resistors as follows: > > > > R1 (pullup) 8.2K ohm > > R2 360 ohm (common value close to 341 ohms) > > R3 360 ohm > > > > So the three possible voltage into the ADC would be: > > > > SW1 0 volts > > SW2 [360/(8200+360)] * 3 volts = 0.042 volts > > > > SW3 [720/(8200+720)] * 3 volts = 0.081 volts > > > > Is this enough differential for reliability and simplified coding? > > Shouldn't I try for more differential by increasing R2 and R3, and > > reducing R1 to keep it all within the 10K ohm limit. Is the 10k > ohm > > ADC > > impedance limitation calculated from the ADC pin to VCC (thru R1) > or > > Ground (thru the other resistors)? > > > > I need some help! > > > > One more thing - one example I found on the internet shows this > kind > > of > > design with a 1 nf (nanofarad I assume) cap between the ADC pin and > > ground. Other examples do not show this. Is this important? > > > > Ransom Peek > > > > > > > > > > ===== > My software has no bugs. Only undocumented features. > > __________________________________ > to unsubscribe, go to http://www.yahoogroups.com and follow the > instructions > Yahoo! Groups Links ===== My software has no bugs. Only undocumented features. __________________________________ |
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RE: Selecting resistor values for 3 pb switches on one ADC input pin - ransom peek - Mar 6 15:25:00 2004
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Now I get it - very clear! Thank you! Ransom -----Original Message----- From: Chad Russel [mailto:] Sent: Saturday, March 06, 2004 11:12 AM To: Subject: RE: [piclist] Selecting resistor values for 3 pb switches on one ADC input pin Input impedance is the resistance the input pin sees. Since VCC and ground are both zero ohms then to either or both. 10K to vcc and 10 K to ground = output impedance of 5K. Any leakage current has to flow through the output impedance. The leakage current developes a voltage which equals an error component. The lower the resistance the lower the error. The 10K maximum number is just a good rule for the +/- 1.0 ua leakage current which = +/- 10 millivolt error. Chad --- ransom peek <> wrote: > Thank you Chad! I will use the 10K, 5K and 20K ohms values as you > advise. You advise that with the pull up resistor at 10k ohms, then > the > input impedance will always be less than 10k. Is the input impedance > measured between I/O pin and ground or VCC? Could you kindly show > how > the math works for this? > > Ransom Peek > > -----Original Message----- > From: Chad Russel [mailto:] > Sent: Thursday, March 04, 2004 7:42 PM > To: > Subject: Re: [piclist] Selecting resistor values for 3 pb switches on > one ADC input pin > > Ok. This method will detect one of three switches, but not multiple > presses. That is a little more complicated and requires 9 bins > instead > of 3. > > Easier for me to look at voltage ratios. With no switches pressed > the > input will be VCC and with SW1 pressed the input will be zero volts. > Easy so far? Now the next trick is to evenly divide the two > remaining > switches. To make life easy set R1 to 10K, then the input impedance > will always be less than 10K. (I can show you the math to nail that > at > 10K max if you want.) > > Next consider SW3 because that will be both resistors in series and > the > next highest voltage which we would like to be 2/3 * Vcc. Make R2 + > R3 > = RA. Then RA/(R1 + RA) = 2/3 > RA = 20K. > > If SW2 is pressed we want a voltage of 1/3 * Vcc > R2/(R1 + R2) = 1/3 > > > R2 = R1/2 > R1 = 5K. > > R1 + R2 = RA so R2 = 15K. > > Check my math. > Chad > > --- ransom peek <> wrote: > > Am trying to read three pushbutton switches with one ADC (16F688) > > input > > pin, using voltage divider method, and need help choosing resistor > > values . There is a Microchip app note showing use of comparator > to > > read multiple switches (capacitor charge timing), but this seems > more > > complicated from a software standpoint. > > > > > > R1 > > -------------/\/\/\/\/\-------- +3V (VCC) > > | > > | > > | > > | R2 > > R3 > > ADC I/O > > > ----------------------/\/\/\/\/\------------------------------/\/\/\/\/\ > > ------- > > | | > > | > > | | > > | > > \ \ > > \ > > SW1 \ SW2 \ > > SW3 \ > > | | > > | > > | | > > | > > GND GND > > GND > > > > > > > > The Microchip 16F688 data sheet advises that for the ADC, the > > "maximum > > recommended impedance for analog sources is 10K ohms". > > > > One (non - Microchip) design note recommends that the divider > network > > slices the range into equal sized "bins", as follows > > : > > BIN SIZE = 2 raised to the # bits in the ADC / # keys scanned. > > > > First choose pull up (R1) resistor value. Then use formula for > > the > > other resistors: > > > > 10 > > So BIN SIZE = 2 / 3 = 1024 / 3 = 341 ohms. > > > > Trade off, I think is lower power usage with higher resistance > > values, > > faster conversion speed for lower values. For my application, will > > poll > > the ADC to read one of three pushbuttons (not simultaneous on). > > > > Need minimum power usage, but not sure if the conversion speed > makes > > any > > difference > > So, my best guess is to choose resistors as follows: > > > > R1 (pullup) 8.2K ohm > > R2 360 ohm (common value close to 341 ohms) > > R3 360 ohm > > > > So the three possible voltage into the ADC would be: > > > > SW1 0 volts > > SW2 [360/(8200+360)] * 3 volts = 0.042 volts > > > > SW3 [720/(8200+720)] * 3 volts = 0.081 volts > > > > Is this enough differential for reliability and simplified coding? > > Shouldn't I try for more differential by increasing R2 and R3, and > > reducing R1 to keep it all within the 10K ohm limit. Is the 10k > ohm > > ADC > > impedance limitation calculated from the ADC pin to VCC (thru R1) > or > > Ground (thru the other resistors)? > > > > I need some help! > > > > One more thing - one example I found on the internet shows this > kind > > of > > design with a 1 nf (nanofarad I assume) cap between the ADC pin and > > ground. Other examples do not show this. Is this important? > > > > Ransom Peek > > > > > > > > > > ===== > My software has no bugs. Only undocumented features. > > __________________________________ > to unsubscribe, go to http://www.yahoogroups.com and follow the > instructions > Yahoo! Groups Links ===== My software has no bugs. Only undocumented features. __________________________________ to unsubscribe, go to http://www.yahoogroups.com and follow the instructions Yahoo! Groups Links |
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RE: Re: Selecting resistor values for 3 pb switches on one ADC input pin - ransom peek - Mar 6 15:25:00 2004
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Thanks Dave. The explanation about how the ADC breaks the incoming voltage value down is especially helpful for me. I am going to go with the ADC mode, three switches, a 10k ohm pull up, and, consistent with Chad’s suggestion, a 5k ohm and a 20k ohm resistor, dividing the voltage into thirds (one switch has no resistor). I will not need to read more than one switch at a time.
Ransom.
-----Original Message-----
I'm not sure it is this
complicated. |
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Re: Selecting resistor values for 3 pb switches on one ADC input pin - Dave Mucha - Mar 6 22:09:00 2004
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--- In , "ransom peek" <ransom.peek@c...> wrote: > Thanks Dave. The explanation about how the ADC breaks the incoming > voltage value down is especially helpful for me. I am going to go with > the ADC mode, three switches, a 10k ohm pull up, and, consistent with > Chad's suggestion, a 5k ohm and a 20k ohm resistor, dividing the voltage > into thirds (one switch has no resistor). I will not need to read more > than one switch at a time. I believe that you will only need to read one switch at a time, but since the audience for the group may want a little more I tend to point out some alternatives. ramble mode is ON....... Also, When designing a project, I look at the bare minimum, then the useful features, then the really cool features and then the maximum possible bunch of c&@p that I can stuff into the darn thing. Obviously the bare minimum is attainable with common sense, the next level of features are things to add if convenient, but the max is always in the back of my mind. I have been known to add silly features at each opportunity and leaving room for them makes sense. At least to me. :) Currently we are working on a data logger. A memory chip, a PIC packaged into a nice case. The idea is to offer people a way to add portable data logging to their applications. Since it is self contained and can work on 4 AA batteries for a couple weeks I figured why not add a couple different power jacks. Chances are we will not use them, but also some user might want the opportunity. Also, since our goal was for 32 data points and the enclosure has some space, I'm hoping that we can find room for a small applications board so the end user can add their circuit directly into our enclosure. We are nearing release for the kits and are looking to make some changes, but the basic unit is done. We reached the Bare Bones phase so that is a DONE. We reached the add a few nifty features stage so that means we are really done for all intent of the original goal. I expect that some users will want things that will get added in as standard features as the product moves in it's life. Just thought you might like to see the thoughts behind the idea how one person looks at a project. Dave ramble mode is OFF |
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