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BOOSTXL-TLV8544PIR: BOOSTXL-TLV8544PIR

Brendan Duggan
Prodigy 60 points
Part Number: BOOSTXL-TLV8544PIR
Other Parts Discussed in Thread: LMC555,

I am trying to connect the BOOSTXL-TLV8544PIR to a LMC555 timer in a mono-stable circuit which runs four leds for 5 sec.  The circuit works fine with one 3 v power supply for the 88544pir module and another 3 v power supply for the leds and lmc555 but if I try one power supply for the entire circuit or if the 555 timer and 8544 module share a battery I have a problem.  The timer self trigger continuously, can make out a flicker in between cycles and thats it..   

  • 0
    TI__Mastermind 24140 points

    Brendan

    My apologies but I’m not understanding what the relationship between the 555 timer and the booster pack is. Are you utilizing a launchpad as well? From your description you have the 8544 circuit working when you power from a separate supply. So it sounds like your hardware is working properly but it sounds like there is some strange interaction when you power a 555 timer from the same supply. Can you explain what you are seeing that is not working when connected? Have you probed the supply line with an oscilloscope when the 8544 is not working?

    Chuck

  • 0 in reply to Chuck Sins
    Prodigy 60 points
    Hi Chuck, I have tried it with launchpad as well as without. I hooked up the osciliscope to the supply line and there are many voltage spikes.

    I'm putting together a PIR sensor circuit that will trigger a 555 timer in monostable and run a set of LEDS for about 5 sec all on a 3v cr2032 button cell battery and than reset until next motion is detected.

    The PIR module I have is a 8845 module from TI that is specifically built for low voltage applications down to 1.8 V.

    The timer is the TI LMC555 good down to 1.8 V as well.

    Im trying to do it all on one button cell but have run into a re triggering issue where the PIR module re fires continuously one 5 sec cycle after another. I can make out a brief glimmer in between each cycle.

    The timer circuit and pir module both act great when not connected to one another. tested independently.

    When PIR Module has its own supply(another 3v) with common ground and the 555 and LEDS have the other 3V supply the system works good.

    When the PIR module and 555 share positive supply and the LEDs has its own supply it has the same triggering problem.

    This makes me think I have a problem with the way my 555 timer is setup. I have experimented what seems like endlessly and just can't seem to get it to work and like I said things work great separately until the 555 and PIR share the same power supply.

    When I run the circuit with two 3V in series I still get the same problem so don't think it is a low voltage problem.
  • 0 in reply to Brendan Duggan
    Prodigy 60 points

    sorry for the multiple posts but can't edit.  The 8845 shows the normal trigger dc shift when the pir is triggered but then it has mini spike randomly every second or so.  I have tried the high, low and analog signals out to the timer circuit with no success.

  • 0 in reply to Brendan Duggan
    TI__Mastermind 24140 points
    Sounds like the output of the 2nd amplifier is oscillating and causing the 2 amps that are being used as comparators to constantly toggle. See if either of the 1st two amplifiers are oscillating. Maybe you could try putting a 1k ohm resistor between the power of 555 timer and the 8544. Since the 555 timer consumes much more power, connect the 555 timer directly to the battery and then connect the 8544 supply pin to the 555 timer supply pin through a 1k resistor. That should decouple the two boards if something is jumping from one circuit to the other. You may also want to put a 10k resistor from the amplifier outputs to the 555 timer. I presume you’re using two timers and are not connecting the two amplifier outputs together.
  • 0 in reply to Chuck Sins
    Prodigy 60 points

    Chuck Sins said:
    Sounds like the output of the 2nd amplifier is oscillating and causing the 2 amps that are being used as comparators to constantly toggle. See if either of the 1st two amplifiers are oscillating. Maybe you could try putting a 1k ohm resistor between the power of 555 timer and the 8544. Since the 555 timer consumes much more power, connect the 555 timer directly to the battery and then connect the 8544 supply pin to the 555 timer supply pin through a 1k resistor. That should decouple the two boards if something is jumping from one circuit to the other. You may also want to put a 10k resistor from the amplifier outputs to the 555 timer. I presume you’re using two timers and are not connecting the two amplifier outputs together.

    Yes, by the looks of the oscilloscope the 2nd amplifier is oscillating which is causing the comparators to toggle.  It usually oscillates right through the 5 seconds that the 555 timer output is on and retriggers the timer... Occasionally the amp settles out but then starts oscillating again caused by the 555's discharge which i see quite strongly on the scope.  Is there a method to correct this on the board or my circuit? Is it a case of there being too much gain on the second amp?

    I tried using the 2nd opamp out, the high comparator and low comparator signal to trigger the timer... all with the same results.  I'm using just one timer and dont have the two comparator signals going to it.

    I tried decoupling without success.

    Any other suggestions?