Author Topic: RF signal activates Simblee.  (Read 158 times)

Wayne

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RF signal activates Simblee.
« on: November 06, 2017, 10:20:48 AM »
Ok, we have failed a test on the Simblee.  The foot switch has 4 buttons other than a test.  2 buttons are a type of switch made by Otto switch (normally open) and 2 are magnetic reed switches.

The test house bombarded the foot switch with RF pulse signals from 385 Mhz to 5.785 Mhz.  The failing area was 704-787 with .2W @ .3m away, 800-960 Mhz @ 2W .3m away.

If the footswitch was facing the antenna with the Save button, it triggered, likewise if the mode was facing the antenna, it triggered.  They also flashed at the pulse rate.
The foot switch sitting horizontal withe the antenna horizontal this happens, if the antenna went vertical, no issues.

The Simblee input is like the boards you buy.  Pin goes high from Vcc to input. The GPIO are 5 and 6 (this board had 14 instead of 5). The inputs have 220 ohm in series to the pin with 10k
on the input side of the switch to ground. 
I'm thinking I might need to put some RF inductors/chokes on each pin used with some caps. Or get a ground plane around the pins.

This area is in the LTE Band 13, 17 and GSM 800/900, Tetra 800, IDEN 820, CDMA 850, and LTE band 5. All cell stuff.

The foot switch acts if the switch is closed, meaning some how RF on the input is making ~ 2 volts or more acting if the switch closed.
Maybe if I switch logic around and do a LOW instead of a HIGH input it might fix it..

Wayne

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Re: RF signal activates Simblee.
« Reply #1 on: November 13, 2017, 12:20:37 PM »
Ok, went to the place today and with a modified board for logic LOW to activate.  Worked like a charm.
But, we have no idea if the housing is causing an issue with ESD.  The older housing is printed ABS plastic and it passes ESD.
The new housing is from a new HP 3D printer which is Nylon. Nylon in itself an issue for static, so we ended up failing the ESD on the switches.
The switches are OTTO switches and IP68 ratings. But they ended up triggering the unit to send.  The shoulder are metal as well as the button.
Thinking that 1, Nylon could possibly play an issue with tracking the ESD pulse to the circuit board. Nylon does have some water in it I understand, nice conductor. ABS no water
2, I simply wire the outside metal to ground. 
We have used these same switches for years with no ESD issues.  So, we are thinking of printing another ABS housing and moving the components to it and seeing the Nylon is the culprit.

Oh, the trigger worked both + and - static charge.  No difference

 

anything