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Re: [Paparazzi-devel] YAPA2 help needed

From: Christophe De Wagter
Subject: Re: [Paparazzi-devel] YAPA2 help needed
Date: Fri, 10 Aug 2012 10:18:53 +0200

Dear Chris,

Sorry to hear about your damaged LPC's. But with any paparazzi board, it is crucial to check every power condition on every pin. In order to save weight and costs, not all pins are hyper-protected.

The yapa has 2 special ADC inputs with space for either a voltage devider or a low pass filter or both together if you stack the SMD capacitor and the resistor but it can also be used to mount a series resistor and some TVS device (Transient Voltage Suppression) or zener. It might not always be ideal because it can in some cases distort the analog signal (and therefore not mounted by default) but it can save LPC's. 


On Fri, Aug 10, 2012 at 9:16 AM, Chris <address@hidden> wrote:
OK now i now what is happening.....
It is quite simple actually, when the current sensor (Sparkfun Attopilot 45A)
is used there is a moment where the current sensing output will overshoot to the sky
because the ESC's capacitors are discharged and that means
that a current of about 150-200 Amps will momentarily flow during the time i first connect the power to the system, causing the current sensor's output to exceed 5v BY FAR and this cause damage to the LPC.
When i was using a 4S pack the capacitor charging surge current is way less.
Also when someone is using the 90A version of this sensor this will not happen because
the current sensing voltage output is halved as the kelvin resistors have half the value of the 45A version i use.
What the current sensor needs  is a zener diode and me a strait jacket :-)


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