Polar Heartrate monitor continuously firing

[NCDR]

When I have wired up my Polar Heartrate Receiver to the FLORA, complete with Neopixel heart display, I find the LEDS are continuously flashing. The sensor band has no effect, whether it is on me or not, or near the receiver or not. Looking at the output of the receiver on a scope I see it is generating continuous streams of 10 msec pulses, at intermittent rates of about 1.2 to 2.5 Hz. It seems the FLORA is picking up these pulses and controlling the neopixels correctly. I assume if the band is not around my chest, the receiver should be indicating no heart beat. Is it broken or am I not using it correctly?

[adafruit_support_mike]

Double-check the battery in the transmitter. If that happens to be low, you can get spurious output.

For that matter, see what the receiver does when the transmitter doesn't have any battery at all. If it still triggers when the transmitter is dead, we'll know to look for other problems.

[NCDR]

The T34 heartrate monitor does not have user-removable or chargeable batteries, at least as far as I can tell. Polar does not have any information on this sensor on their website. The receiver does do the same behavior when the transmitter is more than 50 feet away.

[adafruit_support_mike]

That sounds like a bad receiver.

Send a note to [email protected] with a link to this thread and the folks there will get you a replacement.

[stabbing hobo]

I'm having a similar issue: I've got a Flora with Neopixel 16-ring along with other stuff. If the polar receiver is within ~5 cm of the microcontroller it starts picking up interference. Since the module only gives you pulses, there's no way to filter the noise to get the data you need :/
Taking the thing apart and keeping the receiver separate works, moving it closer makes it go wild.

I tried searching for the chip that's on the board, doesn't seem to be the RMCM-01, which should work in noisy enviroments, this one doesn't seem to.

[adafruit_support_mike]

You're probably getting emitted noise from the NeoPixels. PWM causes lots of sudden changes in current, and a ring is a nearly ideal single-turn inductor.

As Jim Williams once said, "The physicist's solution to interference is distance. The engineer's solution to interference is shielding." Try moving the NeoPixel ring and the receiver as far apart as you can, and if you still have problems try putting a grounded shield between them.