Maximum current into timing pin? - reach m+

Hi, I want to take a signal of known voltage from another source and pass it through the reach m+ timing pin. Problem is I don’t know the current passing through the wire I’m going to use. If I know the voltage then I can drop a resistor in series to guarantee the maximum current. What is the maximum current I can pass to the timing pin without smoking the reach m+?

I want to use a 4v signal and limit it’s current to well below whatever the reach m+ is rated for. Does the m+ have protection circuitry if I’m using 4v instead of 3.3v?

Hi @wsurvey

Please, can I ask you to clarify what pin are you talking about?

Hi Andrew,

I meant Time mark 1 pin.

I want to hook it straight to the LED wire of a UAV to trigger the recording of an event when the LED blinks. I think the LED circuit is about 4V but I have no idea of the current that the circuit can provide. I don’t want to smoke the Reach M+ so i’m wondering if the port has a maximum current rating. If it’s not much then perhaps I have to look at using a relay.

I read in the Reach RTK specifications that the Time Mark input has an over-voltage clamp and a current limiting resistor. Would the Reach M+ also have this kind of protection for the Time Mark 1 pin?

I may be asking the wrong question as I’m an electronics novice.

Hi @wsurvey,

The maximum current for the time mark pin is 3.3V. So, it’s better not to use 4V LED.

Unfortunately, there’s no “protection” on M+ time mark pin.

Can you use the GPIO pins for this solution?
How do you then program the M+ to trigger from the input?

Hi Adam,

I am afraid we can’t guide on how to use GPIO for recording time marks on Reach.

There is nothing in the manual about their use. Why even have them if people can’t use them?

The max voltage of timing pin is 3.3v but what is the input current (50mA, 100mA)?

Hi @mydrones,

There’s no input current. You should set the pin as an “Open drain” and set low logic level for generating time mark.

Also, @tatiana.andreeva provide you with the answer in your other thread.

Thank you @andrew.yushkevich!

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