[neonixie-l] Re: A simple mod for Passive IR sensors... A toggle switch setting clock to: ON / PIR-controlled / Off
A friend made a good point... This mod as originally shown will potentially place +5 or GND directly on a processor GPIO pin. Not a good idea... All of my devices have a series resistor on their PIR input pins - typically 10k. In most cases there are ESD clamps on my designs as well. This is quite possibly not the case on devices you are using. For this reason, I'm adding an optional 2k resistor on the output of the mod schematic. Look at the circuit for any device you are driving with the modified PIR module and decide what value of output resistor makes sense for your device. Consider current driven into the receiving device - especially through input protection diodes. Also watch out for voltage dividers that may be formed with input networks on the target device. Rule one - Ain't nothing simple... (A digression for those interested... Rule 2: If it hasn't been tested it doesn't work. Rule 3: If it hasn't been documented, it hasn't been tested. Rule 4: The lab IS NOT the real world.) That darn rule 1... B -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/eb0a40ce-581d-4b3f-bd40-24dd7a7eb654%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[neonixie-l] Re: A simple mod for Passive IR sensors... A toggle switch setting clock to: ON / PIR-controlled / Off
A friend made a good point by private e-mail... The mod as originally shown will potentially place +5 or GND directly on a processor GPIO pin. Not a good idea... All of my devices have a series resistor on their PIR input pins - typically 10k. In most cases there are ESD clamps on my designs as well. A pull-down to assure no false triggering is also present on some of my clocks. One or more of these are quite possibly not the case for devices you are using. For this reason, consider adding a series resistor on the output of the modified PIR detector downstream of the switch. Look at the input circuit for any device you are driving with the modified PIR module and decide what value of output resistors on the module make sense for your device. Consider current driven into the receiving device - especially through input protection diodes. Also watch out for voltage dividers that may be formed with input networks on the target device - as an example, there might be a pull-down or pull-up on the connected device input to prevent false triggering. 2K into a 10k pull-down meets minimum voltage high and low levels on one of my clocks. (Try sending PIR and true RS-232 down a shared cable... The cap coupling from GPS data edges in the cable can be enough to trigger a PIR input without a modest pull-down. Ask me how I know?) Rule one - Ain't nothing simple... (A digression for those interested... Rule 2: If it hasn't been tested, it doesn't work. Rule 3: If it hasn't been documented, it hasn't been tested. (True in several regulated industries...) Rule 4: The lab IS NOT the real world.) That darn rule 1... B -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/422d16b9-733a-4a08-a12d-bfd502b52207%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[neonixie-l] Re: A simple mod for Passive IR sensors... A toggle switch setting clock to: ON / PIR-controlled / Off
Most PIR sensors should run on 3.3V; most likely yours is one of those 'jelly bean' units available from dozens of sellers on Ebay/Amazon. If there are 3.3V devices in your clock, there will be a 3.3V source somewhere; In my case I provide +5V to a RasPi, but it's onboard 3.3V regulator's output is exposed, so it's used to power the PIR sensor, which requires less than 1mA of current. -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/f313bf55-526f-4b6a-b132-57107357262d%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
[neonixie-l] Re: A simple mod for Passive IR sensors... A toggle switch setting clock to: ON / PIR-controlled / Off
A friend made a good point by private e-mail... The mod as originally shown will potentially place +5 or GND directly on a processor GPIO pin. Not a good idea... All of my devices have a series resistor on their PIR input pins - typically 10k. In most cases there are ESD clamps on my designs as well. A pull-down to assure no false triggering is also present on some of my clocks. One or more of these are quite possibly not the case for devices you are using. For this reason, consider adding a series resistor on the output of the modified PIR detector downstream of the switch. Look at the input circuit for any device you are driving with the modified PIR module and decide what value of output resistors on the module make sense for your device. Consider current driven into the receiving device - especially through input protection diodes. Also watch out for voltage dividers that may be formed with input networks on the target device - as an example, there might be a pull-down or pull-up on the connected device input to prevent false triggering. 2K into a 10k pull-down meets minimum voltage high and low levels on one of my clocks. (Try sending PIR and true RS-232 down a shared cable... The cap coupling from GPS data edges in the cable can be enough to trigger a PIR input without a modest pull-down. Ask me how I know?) B > -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to neonixie-l+unsubscr...@googlegroups.com. To post to this group, send an email to neonixie-l@googlegroups.com. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/e3f60396-f6be-4b4d-8e4a-178e5bc20ef4%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.