Initializing Brushless Motor problem

Hello, I hope you can help me. I'm using Google translator, I do not speak good English. I'm doing a quadcopter and there is something I do not understand. I used a library to control servos and have it modified to run the motor with ESC. The problem is as follows: - If I connect the Netduino and then connect the ESC to the battery everything works fine. - But if I connect two devices at once from the beginning, the ESC does not start well. Does not beep it is connected. Must always be the Netduino already connected before power is applied to the ESC. This is correct and should control it with a relay or something that escapes me.

I think that the netduino outputs all go high for a period during reset. This is probably being seen as the throttle not at zero by the ESC. I think most ESCs must be connected with the throttle at zero or they won't work. This is for obvious safety reasons. You could need to use some external gate to block the PWM output from the ESC until you are ready to output a proper servo command signal. Since you have 4 ESC outputs maybe use a quad XOR gate with 1 input of each gate connected together to another output pin that functions as an enable when it is low? This has the advantage of also buffering the servo signals from 3.3 up to 5 volts if you choose.

You could need to use some external gate to block the PWM output

Or add external pull-down resistors to keep the pins low during Netduino startup.

A pull down resistor will do it. I had a similar problems with relays from the Netduino on startup. The internal pull-up resistor was enough to cause the relays to operate until my code defined them as an output. Obviously Mike P's suggestion of XOR gates will work too if that suits your design better.

Thank you very much everyone. I'll try it from the pull-up resistance (when I return from vacation) I think the easiest option.

After holidays and other things yesterday I tried again yesterday. I tested with a pull-up and Pull-Down but got nothing. I want to try the solution of a relay. The scheme I think I have clear (which is attached). - Would have a switch that would do is control the supply circuit of Netduino. - The program would start and once the program is initialized activate the digital output that in turn activate the relay, closing the supply circuit of ESC. Well, I think this is simple. My problem is that I have begun to look relays and i don't know what I need. The ESC's that I have are 18 A each. Ideally, a relay to feed the 4 ESC's that I have. I've been looking relays and I find specifications such as: - Relay coil 12V CC, 6A 250V CA/30V CC - Relay coil 12V CC, 1A 220V - Signal relay 5V G5V-1, 24V G5V-1 - ... Come on, I have no idea that specifications must have the relay I need. - When talking about going to 12V, 5V or refers to is the voltage at which "closes" the relay? - Puts the maximum power for AC. How is DC? I'm afraid to put a hold not need as many as possible amperior 4 ESC's Thank you. (translated with google, sorry)

Yes coil voltage is the voltage neccessary to close the relay. You'll want to try and find SSR models (solid-state-relays), normal relays are mechanical and can cause noise on the line. Ideally you want one that triggers at 3.3v, and under 16ma of current, so you could drive it right off a netduino pin. On the other side it needs to handle DC voltages matching your motors, and should be rated to a max current near the max current your motors can draw to be safe.

Could do better with thyristors? The engines go directly to the 11.1 V battery and I think that each engine at full power consumes about 16 A Which of these would be nice? http://www.micropik....g_ci_triacs.htm

I'm also building a quad, but haven't wired up a solution to your issue yet, triacs may work, I have some and was planning to try it. For now I 'boot' the netduino with a USB cable then connect the main battery, then unplug the usb. You could consider using a separate power supply for the netduino, to isolate it from the motors.