I have two PoC units. Both devices make use of a standalone accelerometer (Bosch BMA250 Dedicated mode C).
The first device senses motion and interrupts the continuity between ‘voltage-free’ (almost) inputs on the radio. Interrupt pin on accelerometer pulls high which engages a relay via a bc547. (load: relay, 3v, 9.2mA)
The second device senses motion and alerts by beeping as well as sending a radio signal. Again, interrupt pin pulls high when in motion which makes the bc547 engage the buzzer circuit. (load: buzzer, 9v, 7mA)
The buzzer could do with engaging for a second or two after the motion signal pull low to make it more noticeable.
The relay could do with engaging for a second or two after the motion signal is pulled low because the debounce on our radio appears to be more severe than spec (it is ignoring brief movements).
I want to use a mic1555 in monostable mode to do this but it appears to require the input to be pulled low during alert state, whereas I have a pull high in that situation.
I got a smitt trigger inverter to act as a not gate to get the right input to the 555 but not working.
1. Is there a simpler way to achieve the delay?
2. Does a low power shmitt-trigger inverter have capacitor/resistor internally? The Texas instrument data sheet is vague/over my head.
Many thanks,
Ben.
(Moderator's note: font size and attributes Edited for readability)
The first device senses motion and interrupts the continuity between ‘voltage-free’ (almost) inputs on the radio. Interrupt pin on accelerometer pulls high which engages a relay via a bc547. (load: relay, 3v, 9.2mA)
The second device senses motion and alerts by beeping as well as sending a radio signal. Again, interrupt pin pulls high when in motion which makes the bc547 engage the buzzer circuit. (load: buzzer, 9v, 7mA)
The buzzer could do with engaging for a second or two after the motion signal pull low to make it more noticeable.
The relay could do with engaging for a second or two after the motion signal is pulled low because the debounce on our radio appears to be more severe than spec (it is ignoring brief movements).
I want to use a mic1555 in monostable mode to do this but it appears to require the input to be pulled low during alert state, whereas I have a pull high in that situation.
I got a smitt trigger inverter to act as a not gate to get the right input to the 555 but not working.
1. Is there a simpler way to achieve the delay?
2. Does a low power shmitt-trigger inverter have capacitor/resistor internally? The Texas instrument data sheet is vague/over my head.
Many thanks,
Ben.
(Moderator's note: font size and attributes Edited for readability)
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