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2012-10-09 by Elham B
noise!!! my project is with micro avr,atmega32. pinD.3 , external interrupt ,operating uncaused!! because of noise!! I deriving a dc motor in the interrupt , i using capacitors in every where that was nesseccery for solving this problem... pleesssee help meeeee :-( what can i do????
2012-10-10 by Jim Wagner
There is not enough information to provide any help. What is PD3 connected to? Why do you have an interrupt for PD3? What do you mean by "operating uncaused"? Every action must have a cause! What do you mean by "driving a dc motor in the interrupt"? (I assume you mean driving instead of deriving). Jim Wagner Oregon Research Electronics On Oct 9, 2012, at 12:50 PM, Elham B wrote: > noise!!! > my project is with micro avr,atmega32. > pinD.3 , external interrupt ,operating uncaused!! > because of noise!! > I deriving a dc motor in the interrupt , > i using capacitors in every where that was nesseccery for solving this problem... > pleesssee help meeeee :-( > what can i do???? > > [Non-text portions of this message have been removed]
2012-10-10 by Zack Widup
I am guessing he means by "operating uncaused" that the interrupt is getting interrupted unintentionally by the noise, i.e. what is supposed to cause the interrupt is not what is causing it. Also, yes, I think he means driving a DC motor. If there's a motor involved, there's likely to be noise. Without seeing the circuit, it's hard to say what's happening. The group doesn't allow attachments, so if one was attached it didn't make it. It is best to upload the attachment into the files or photos section of the webpage. Some inductors may be needed for filtering as well as capacitors. Zack
On 10/10/12, Jim Wagner <wagnejam99@comcast.net> wrote: > There is not enough information to provide any help. > > What is PD3 connected to? > > Why do you have an interrupt for PD3? > > What do you mean by "operating uncaused"? Every action must have a cause! > > What do you mean by "driving a dc motor in the interrupt"? (I assume you > mean driving instead of deriving). > > Jim Wagner > Oregon Research Electronics > > On Oct 9, 2012, at 12:50 PM, Elham B wrote: > >> noise!!! >> my project is with micro avr,atmega32. >> pinD.3 , external interrupt ,operating uncaused!! >> because of noise!! >> I deriving a dc motor in the interrupt , >> i using capacitors in every where that was nesseccery for solving this >> problem... >> pleesssee help meeeee :-( >> what can i do???? >> >> > > > > [Non-text portions of this message have been removed] > > > > ------------------------------------ > > Yahoo! Groups Links > > > >
2012-10-10 by Elham B
an ultrasonic module connected to interrupt, i upload the attachment into the photos,,, in this circuit dc motor connected to micro,,if output of ultrasonic pull down the INT1 ,dc motor running...but the interrupt is getting interrupted unintentionally by the noise what's happening??? ________________________________
From: Jim Wagner <wagnejam99@comcast.net> To: AVR-Chat@yahoogroups.com Sent: Wednesday, October 10, 2012 8:58 AM Subject: Re: [AVR-Chat] noise problem There is not enough information to provide any help. What is PD3 connected to? Why do you have an interrupt for PD3? What do you mean by "operating uncaused"? Every action must have a cause! What do you mean by "driving a dc motor in the interrupt"? (I assume you mean driving instead of deriving). Jim Wagner Oregon Research Electronics On Oct 9, 2012, at 12:50 PM, Elham B wrote: > noise!!! > my project is with micro avr,atmega32. > pinD.3 , external interrupt ,operating uncaused!! > because of noise!! > I deriving a dc motor in the interrupt , > i using capacitors in every where that was nesseccery for solving this problem... > pleesssee help meeeee :-( > what can i do???? > > [Non-text portions of this message have been removed] ------------------------------------ Yahoo! Groups Links [Non-text portions of this message have been removed]
2012-10-10 by Zack Widup
Hi Elham, There are several things that may be causing the problem and several things you can do to try to prevent it. I am assuming that the motor draws a fair amount of current, since you're driving it with some fairly good-sized FET's. I would not acquire the voltage to power the ultrasonic module or the AVR from the same power supply that provides 12-volt power for the motor. Also, is the wire between the ultrasonic module and the AVR circuit shielded? You might want to try a shielded wire (with the shield grounded) on this line. Also, bypass the power for the module and the AVR with several capacitors in parallel - maybe a few microfarads in parallel with a 1000 pF and a 10 pF. This would cover a wide frequency range of noise that may be getting into the circuit. Also, you can enclose the AVR circuit in a metal case and bring the "Input A" and "Input B" leads out through bypass capacitors. Maybe you have tried some of these already? Do you have an oscilloscope? I would look at the waveform on the lead to PD3 to see how clean it actually is. Zack On Wed, Oct 10, 2012 at 2:49 PM, Elham B <elhamb88@ymail.com> wrote: > ** > > > an ultrasonic module connected to interrupt, > i upload the attachment into the photos,,, > in this circuit dc motor connected to micro,,if output of ultrasonic pull > down the INT1 ,dc motor running...but the interrupt is > > getting interrupted unintentionally by the noise > what's happening??? > > ________________________________ > From: Jim Wagner <wagnejam99@comcast.net> > To: AVR-Chat@yahoogroups.com > Sent: Wednesday, October 10, 2012 8:58 AM > Subject: Re: [AVR-Chat] noise problem > > > There is not enough information to provide any help. > > What is PD3 connected to? > > Why do you have an interrupt for PD3? > > What do you mean by "operating uncaused"? Every action must have a cause! > > What do you mean by "driving a dc motor in the interrupt"? (I assume you > mean driving instead of deriving). > > Jim Wagner > Oregon Research Electronics > > On Oct 9, 2012, at 12:50 PM, Elham B wrote: > > > noise!!! > > my project is with micro avr,atmega32. > > pinD.3 , external interrupt ,operating uncaused!! > > because of noise!! > > I deriving a dc motor in the interrupt , > > i using capacitors in every where that was nesseccery for solving this > problem... > > pleesssee help meeeee :-( > > what can i do???? > > > > > > [Non-text portions of this message have been removed] > > ------------------------------------ > > Yahoo! Groups Links > > [Non-text portions of this message have been removed] > > > [Non-text portions of this message have been removed]
2012-10-10 by Elham B
i see waveform in the oscilloscope,,,there is pulse on pinD.3 ________________________________
From: Zack Widup <w9sz.zack@gmail.com> To: AVR-Chat@yahoogroups.com Sent: Wednesday, October 10, 2012 11:30 PM Subject: Re: [AVR-Chat] noise problem Hi Elham, There are several things that may be causing the problem and several things you can do to try to prevent it. I am assuming that the motor draws a fair amount of current, since you're driving it with some fairly good-sized FET's. I would not acquire the voltage to power the ultrasonic module or the AVR from the same power supply that provides 12-volt power for the motor. Also, is the wire between the ultrasonic module and the AVR circuit shielded? You might want to try a shielded wire (with the shield grounded) on this line. Also, bypass the power for the module and the AVR with several capacitors in parallel - maybe a few microfarads in parallel with a 1000 pF and a 10 pF. This would cover a wide frequency range of noise that may be getting into the circuit. Also, you can enclose the AVR circuit in a metal case and bring the "Input A" and "Input B" leads out through bypass capacitors. Maybe you have tried some of these already? Do you have an oscilloscope? I would look at the waveform on the lead to PD3 to see how clean it actually is. Zack On Wed, Oct 10, 2012 at 2:49 PM, Elham B <elhamb88@ymail.com> wrote: > ** > > > an ultrasonic module connected to interrupt, > i upload the attachment into the photos,,, > in this circuit dc motor connected to micro,,if output of ultrasonic pull > down the INT1 ,dc motor running...but the interrupt is > > getting interrupted unintentionally by the noise > what's happening??? > > ________________________________ > From: Jim Wagner <wagnejam99@comcast.net> > To: AVR-Chat@yahoogroups.com > Sent: Wednesday, October 10, 2012 8:58 AM > Subject: Re: [AVR-Chat] noise problem > > > There is not enough information to provide any help. > > What is PD3 connected to? > > Why do you have an interrupt for PD3? > > What do you mean by "operating uncaused"? Every action must have a cause! > > What do you mean by "driving a dc motor in the interrupt"? (I assume you > mean driving instead of deriving). > > Jim Wagner > Oregon Research Electronics > > On Oct 9, 2012, at 12:50 PM, Elham B wrote: > > > noise!!! > > my project is with micro avr,atmega32. > > pinD.3 , external interrupt ,operating uncaused!! > > because of noise!! > > I deriving a dc motor in the interrupt , > > i using capacitors in every where that was nesseccery for solving this > problem... > > pleesssee help meeeee :-( > > what can i do???? > > > > > > [Non-text portions of this message have been removed] > > ------------------------------------ > > Yahoo! Groups Links > > [Non-text portions of this message have been removed] > > > [Non-text portions of this message have been removed] ------------------------------------ Yahoo! Groups Links [Non-text portions of this message have been removed]
2012-10-10 by Elham B
you offer to using 1000pf & 10pf capacitor in my circuit? ________________________________
From: Zack Widup <w9sz.zack@gmail.com> To: AVR-Chat@yahoogroups.com Sent: Wednesday, October 10, 2012 11:30 PM Subject: Re: [AVR-Chat] noise problem Hi Elham, There are several things that may be causing the problem and several things you can do to try to prevent it. I am assuming that the motor draws a fair amount of current, since you're driving it with some fairly good-sized FET's. I would not acquire the voltage to power the ultrasonic module or the AVR from the same power supply that provides 12-volt power for the motor. Also, is the wire between the ultrasonic module and the AVR circuit shielded? You might want to try a shielded wire (with the shield grounded) on this line. Also, bypass the power for the module and the AVR with several capacitors in parallel - maybe a few microfarads in parallel with a 1000 pF and a 10 pF. This would cover a wide frequency range of noise that may be getting into the circuit. Also, you can enclose the AVR circuit in a metal case and bring the "Input A" and "Input B" leads out through bypass capacitors. Maybe you have tried some of these already? Do you have an oscilloscope? I would look at the waveform on the lead to PD3 to see how clean it actually is. Zack On Wed, Oct 10, 2012 at 2:49 PM, Elham B <elhamb88@ymail.com> wrote: > ** > > > an ultrasonic module connected to interrupt, > i upload the attachment into the photos,,, > in this circuit dc motor connected to micro,,if output of ultrasonic pull > down the INT1 ,dc motor running...but the interrupt is > > getting interrupted unintentionally by the noise > what's happening??? > > ________________________________ > From: Jim Wagner <wagnejam99@comcast.net> > To: AVR-Chat@yahoogroups.com > Sent: Wednesday, October 10, 2012 8:58 AM > Subject: Re: [AVR-Chat] noise problem > > > There is not enough information to provide any help. > > What is PD3 connected to? > > Why do you have an interrupt for PD3? > > What do you mean by "operating uncaused"? Every action must have a cause! > > What do you mean by "driving a dc motor in the interrupt"? (I assume you > mean driving instead of deriving). > > Jim Wagner > Oregon Research Electronics > > On Oct 9, 2012, at 12:50 PM, Elham B wrote: > > > noise!!! > > my project is with micro avr,atmega32. > > pinD.3 , external interrupt ,operating uncaused!! > > because of noise!! > > I deriving a dc motor in the interrupt , > > i using capacitors in every where that was nesseccery for solving this > problem... > > pleesssee help meeeee :-( > > what can i do???? > > > > > > [Non-text portions of this message have been removed] > > ------------------------------------ > > Yahoo! Groups Links > > [Non-text portions of this message have been removed] > > > [Non-text portions of this message have been removed] ------------------------------------ Yahoo! Groups Links [Non-text portions of this message have been removed]
2012-10-10 by Jim Wagner
What happens if you disconnect the output of your sensor from the MCU board. Then, look at the ultrasonic output with your scope. Is the pulse there or not there? It may be that the problem is entirely in the sensor! Jim Wagner
----- Original Message ----- From: "Elham B" <elhamb88@ymail.com> To: AVR-Chat@yahoogroups.com Sent: Wednesday, October 10, 2012 12:49:25 PM Subject: Re: [AVR-Chat] noise problem an ultrasonic module connected to interrupt, i upload the attachment into the photos,,, in this circuit dc motor connected to micro,,if output of ultrasonic pull down the INT1 ,dc motor running...but the interrupt is getting interrupted unintentionally by the noise what's happening??? ________________________________ From: Jim Wagner < wagnejam99@comcast.net > To: AVR-Chat@yahoogroups.com Sent: Wednesday, October 10, 2012 8:58 AM Subject: Re: [AVR-Chat] noise problem There is not enough information to provide any help. What is PD3 connected to? Why do you have an interrupt for PD3? What do you mean by "operating uncaused"? Every action must have a cause! What do you mean by "driving a dc motor in the interrupt"? (I assume you mean driving instead of deriving). Jim Wagner Oregon Research Electronics On Oct 9, 2012, at 12:50 PM, Elham B wrote: > noise!!! > my project is with micro avr,atmega32. > pinD.3 , external interrupt ,operating uncaused!! > because of noise!! > I deriving a dc motor in the interrupt , > i using capacitors in every where that was nesseccery for solving this problem... > pleesssee help meeeee :-( > what can i do???? > > [Non-text portions of this message have been removed] ------------------------------------ Yahoo! Groups Links [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
2012-10-11 by bayramdavies
--- In AVR-Chat@yahoogroups.com, Zack Widup <w9sz.zack@...> wrote: > .. bypass the power ... with several > capacitors in parallel - maybe a few > microfarads in parallel with a 1000 > pF and a 10 pF. Using different values of capacitors in parallel for high-frequency bypass is not a good idea. The smaller capacitors can form parallel resonant circuits with the parasitic inductance of the larger capacitors and increase the impedance at high frequency. The way to do it is to use one sufficiently large capacitor with the lowest practical parasitic impedance and pay close attention to parasitics in routing. You can, of course, add an electrolytic somewhere or other to help with low-frequency stability. Graham.
2012-10-11 by Zack Widup
Hmm ... this technique is extensively used in UHF and microwave circuits. You will often see two or three bypass capacitors of different values at each point where a power lead or trace approaches an active device. Zack On Thu, Oct 11, 2012 at 7:59 AM, bayramdavies <Yahoo37849@ecrostech.com>wrote: > ** > > > --- In AVR-Chat@yahoogroups.com, Zack Widup <w9sz.zack@...> wrote: > > > .. bypass the power ... with several > > > capacitors in parallel - maybe a few > > microfarads in parallel with a 1000 > > pF and a 10 pF. > > Using different values of capacitors in parallel for high-frequency bypass > is not a good idea. The smaller capacitors can form parallel resonant > circuits with the parasitic inductance of the larger capacitors and > increase the impedance at high frequency. The way to do it is to use one > sufficiently large capacitor with the lowest practical parasitic impedance > and pay close attention to parasitics in routing. > > You can, of course, add an electrolytic somewhere or other to help with > low-frequency stability. > > Graham. > > > [Non-text portions of this message have been removed]
2012-10-11 by David VanHorn
On Wed, Oct 10, 2012 at 2:59 PM, Jim Wagner <wagnejam99@comcast.net> wrote: > What happens if you disconnect the output of your sensor from the MCU board. Then, look at the ultrasonic output with your scope. Is the pulse there or not there? It may be that the problem is entirely in the sensor! It is entirely possible that the motor is radiating ultrasonic noise that is being picked up by the sensor.
2012-10-11 by Jim Wagner
That was my point - to determine the origin of the interrupt signal. Jim Wagner
----- Original Message ----- From: "David VanHorn" <microbrix@gmail.com> To: AVR-Chat@yahoogroups.com Sent: Thursday, October 11, 2012 8:26:06 AM Subject: Re: [AVR-Chat] noise problem On Wed, Oct 10, 2012 at 2:59 PM, Jim Wagner < wagnejam99@comcast.net > wrote: > What happens if you disconnect the output of your sensor from the MCU board. Then, look at the ultrasonic output with your scope. Is the pulse there or not there? It may be that the problem is entirely in the sensor! It is entirely possible that the motor is radiating ultrasonic noise that is being picked up by the sensor. [Non-text portions of this message have been removed]
2012-10-11 by bayramdavies
Zack, Yes, it is extensively used in digital circuits too, but it's a bad idea. The analysis that proved to me that it was a bad idea was done in the context of using surface-mount ceramic chip capacitors in the bypassing of digital circuits. I don't know if there are other considerations for UHF and microwave. Also, years ago you could only get small values in the smallest, low inductance, packages, so there was a counter-argument for paralleling different values. A modern ceramic chip capacitor has a parasitic inductance of no more than the equivalent-sized piece of wire. You can get 0.1uF and higher values in 0402 size. The effectiveness of such a bypass capacitor is usually determined by how you connect it to the device pins and power and ground planes. Graham. --- In AVR-Chat@yahoogroups.com, Zack Widup <w9sz.zack@...> wrote:
> > Hmm ... this technique is extensively used in UHF and microwave circuits. > You will often see two or three bypass capacitors of different values at > each point where a power lead or trace approaches an active device. > > Zack > > On Thu, Oct 11, 2012 at 7:59 AM, bayramdavies <Yahoo37849@...>wrote: > > > ** > > > > > > --- In AVR-Chat@yahoogroups.com, Zack Widup <w9sz.zack@> wrote: > > > > > .. bypass the power ... with several > > > > > capacitors in parallel - maybe a few > > > microfarads in parallel with a 1000 > > > pF and a 10 pF. > > > > Using different values of capacitors in parallel for high-frequency bypass > > is not a good idea. The smaller capacitors can form parallel resonant > > circuits with the parasitic inductance of the larger capacitors and > > increase the impedance at high frequency. The way to do it is to use one > > sufficiently large capacitor with the lowest practical parasitic impedance > > and pay close attention to parasitics in routing. > > > > You can, of course, add an electrolytic somewhere or other to help with > > low-frequency stability. > > > > Graham.
2012-10-12 by Leon
--- In AVR-Chat@yahoogroups.com, "bayramdavies" <Yahoo37849@...> wrote: > > --- In AVR-Chat@yahoogroups.com, Zack Widup <w9sz.zack@> wrote: > > > .. bypass the power ... with several > > capacitors in parallel - maybe a few > > microfarads in parallel with a 1000 > > pF and a 10 pF. > > Using different values of capacitors in parallel for high-frequency bypass is not a good idea. The smaller capacitors can form parallel resonant circuits with the parasitic inductance of the larger capacitors and increase the impedance at high frequency. The way to do it is to use one sufficiently large capacitor with the lowest practical parasitic impedance and pay close attention to parasitics in routing. As many as three capacitors per pin are recommended by Xylinx and Altera for decoupling FPGAs! Leon
2012-10-14 by David V
Larger caps can still have relatively large impedance. I wouldn't try to bypass my 2GHz radios with a 0.1uF. Critical also is the routing. I try hard to have the power come to the pad and then away from the pad, not a "T" connection that runs down to the pad. Little things like that can put you in the category of "Is that thing on?" at emissions testing. :) (two layers, no enclosure, no ferrites, shields or other voodoo)
2012-10-14 by Bob Paddock
On Thu, Oct 11, 2012 at 6:08 PM, bayramdavies <Yahoo37849@ecrostech.com> wrote: > Yes, it is extensively used in digital circuits too, but it's a bad idea. The analysis that proved to me that it was a bad idea was done in the context of using surface-mount ceramic chip capacitors in the bypassing of digital circuits. I don't know if there are other considerations for UHF and microwave. Also, years ago you could only get small values in the smallest, low inductance, packages, so there was a counter-argument for paralleling different values. > > A modern ceramic chip capacitor has a parasitic inductance of no more than the equivalent-sized piece of wire. You can get 0.1uF and higher >values in 0402 size. The effectiveness of such a bypass capacitor is usually determined by how you connect it to the device pins and power and >ground planes. It has to do with the self-resonance of the package. Different capacitance values may have the same package self-resonance, for packages of the same size: http://www.sigcon.com/Pubs/news/1_17.htm Summed up in Intersil App. Note 1325: http://www.intersil.com/data/an/an1325.pdf "Since the same package was used for each of the capacitors, their high frequency responses are the same. Effectively, this negates the use of the smaller capacitors!" Articles by Howard Jonson on the subject: http://www.sigcon.com/Pubs/pubsKeyword.htm#bypass%20capacitors For anyone that is really into this kind of stuff I *STRONGLY* recommended subscribing to the Compliance Club, and reading all 102 (current issue) back issues: Journal Issue #55 and #56 2004 explains the issue and the issues of layout that I've never seen described anyplace else: http://www.compliance-club.com/journal_article.aspx?artid=138 section 2.6 to 2.9. [Note the pop-up at the bottom of the screen that forces you to check a box to allow cookies, if you don't you can't subscribe.] Every layout I've ever seen puts the different values capacitors in the same physical orientation next to each other. This fails to account for magnetic flux interference between the packages. Self-resonance (package), ESR, ESL, capacitance value, magnetic flux (layout), frequencies of interest, number of board layers, all have to be accounted for, which means it is not as easy as paralleled values is good or paralleled values is bad. Makes this job such fun... -- http://blog.softwaresafety.net/ http://www.designer-iii.com/ http://www.wearablesmartsensors.com/
2012-10-14 by farshid alipour
have you used pull-up or pull-down resistor on the interrupt pin ? [Non-text portions of this message have been removed]
2012-10-14 by Elham B
i use pull-down resistor ________________________________
From: farshid alipour <farshid32001@yahoo.com> To: AVR-Chat@yahoogroups.com Sent: Sunday, October 14, 2012 11:26 PM Subject: Re: [AVR-Chat] noise problem have you used pull-up or pull-down resistor on the interrupt pin ? [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
2012-10-14 by farshid alipour
how much is it ?if the resistor is too big noise can effect on it .are you sure the out put of the module is digital ? --- On Sun, 10/14/12, Elham B <elhamb88@ymail.com> wrote:
From: Elham B <elhamb88@ymail.com>
Subject: Re: [AVR-Chat] noise problem
To: "AVR-Chat@yahoogroups.com" <AVR-Chat@yahoogroups.com>
Date: Sunday, October 14, 2012, 11:38 PM
i use pull-down resistor
________________________________
From: farshid alipour <farshid32001@yahoo.com>
To: AVR-Chat@yahoogroups.com
Sent: Sunday, October 14, 2012 11:26 PM
Subject: Re: [AVR-Chat] noise problem
have you used pull-up or pull-down resistor on the interrupt pin ?
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]
[Non-text portions of this message have been removed]2012-10-15 by Elham B
1k,,yes it's digital ________________________________
From: farshid alipour <farshid32001@yahoo.com> To: AVR-Chat@yahoogroups.com Sent: Monday, October 15, 2012 12:21 AM Subject: Re: [AVR-Chat] noise problem how much is it ?if the resistor is too big noise can effect on it .are you sure the out put of the module is digital ? --- On Sun, 10/14/12, Elham B <elhamb88@ymail.com> wrote: From: Elham B <elhamb88@ymail.com> Subject: Re: [AVR-Chat] noise problem To: "AVR-Chat@yahoogroups.com" <AVR-Chat@yahoogroups.com> Date: Sunday, October 14, 2012, 11:38 PM i use pull-down resistor ________________________________ From: farshid alipour <farshid32001@yahoo.com> To: AVR-Chat@yahoogroups.com Sent: Sunday, October 14, 2012 11:26 PM Subject: Re: [AVR-Chat] noise problem have you used pull-up or pull-down resistor on the interrupt pin ? [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed] [Non-text portions of this message have been removed]
2012-10-18 by R E Purcella
the Atmel documentation calls for higher value pull up or pull down resistors, usually 20K. however 10K work fine. But 1K is a bit low. I'm still not understanding what noise you are having. If it is digital in nature is it noise?, or Do you have your external interrupt being triggered because the port is set as an output? (part of the external interrupt nature) rep
On 10/15/2012 12:59 AM, Elham B wrote: > > 1k,,yes it's digital > > ________________________________ > From: farshid alipour <farshid32001@yahoo.com > <mailto:farshid32001%40yahoo.com>> > To: AVR-Chat@yahoogroups.com <mailto:AVR-Chat%40yahoogroups.com> > Sent: Monday, October 15, 2012 12:21 AM > Subject: Re: [AVR-Chat] noise problem > > > > how much is it ?if the resistor is too big noise can effect on it .are > you sure the out put of the module is digital ? > > --- On Sun, 10/14/12, Elham B <elhamb88@ymail.com > <mailto:elhamb88%40ymail.com>> wrote: > > From: Elham B <elhamb88@ymail.com <mailto:elhamb88%40ymail.com>> > Subject: Re: [AVR-Chat] noise problem > To: "AVR-Chat@yahoogroups.com <mailto:AVR-Chat%40yahoogroups.com>" > <AVR-Chat@yahoogroups.com <mailto:AVR-Chat%40yahoogroups.com>> > Date: Sunday, October 14, 2012, 11:38 PM > > > > i use pull-down resistor > > ________________________________ > > From: farshid alipour <farshid32001@yahoo.com > <mailto:farshid32001%40yahoo.com>> > > To: AVR-Chat@yahoogroups.com <mailto:AVR-Chat%40yahoogroups.com> > > Sent: Sunday, October 14, 2012 11:26 PM > > Subject: Re: [AVR-Chat] noise problem > > > > have you used pull-up or pull-down resistor on the interrupt pin ? > > [Non-text portions of this message have been removed] > > [Non-text portions of this message have been removed] > > [Non-text portions of this message have been removed] > > [Non-text portions of this message have been removed] > >
2012-10-18 by Clark Martin
On Oct 17, 2012, at 8:38 PM, R E Purcella wrote: > the Atmel documentation calls for higher value pull up or pull down > resistors, usually 20K. however 10K work fine. But 1K is a bit low. Unless the AVR pin is driving the resistor, high or low, it doesn't matter to the AVR how low the resistor is. If the resistor is too low the device driving it may not be able to pull it low enough or it may be overloaded. The other factor is how much power the resistor dissipates. 1K used to be a common value as a pull up resistor but it's 5 mA (Vcc = 5V) may well be more than the rest of the circuit. I have been using either an external 100K resistor or the AVR built in pull up of 30K. [Non-text portions of this message have been removed]