Cape powers off when the propeller motors are started


#1

I have a live video feed coming in from the UI. I can control the leds and servo. When I try to run the propellers from the UI, There is a slight rattling sound at the propeller motors as they start but immediately the green and the red leds on the cape go off momentarily and the motors stop. My connection to the rov gets disrupted. The green light on the cape comes back on immediately and the red after a couple of seconds.

Any ideas on what could be causing this?

My guess is that when the motor starts, the escs draw all the power and the voltage to the cape drops substantially resulting in powering off of the cape.

I haven't yet tested if my theory is correct. I plan to use two power sources, one for the escs and other for the board and see if that works.

From the screw terminals, I am using 18 gauge stranded wires to connect to the escs and 22 gauge solid core wire to connect to the cape.

Could the difference in resistance between the wires cause the power to shut out to the board?

I tried replacing the 22 gauge wire to the cape with a thicker wire but the terminal posts on the cape is not accommodating a thicker wire.

Any thoughts?


#2

Have you programmed the ESCs correctly?

http://wiki.openrov.com/index.php/Programming_the_ESC


#3

Thanks, I haven't programmed the escs yet.


#4

Actually, I would guess that you're powering your ROV with standard Alkaline C batteries. If that's the case, this is a known issue. It turns out that Alkaline C's have a high internal resistance which only allows them to source a few amps. If you switch to NiMH C's (which have a lower internal resistance and can thus source more current) that should take care of the problem. Keep in mind though that NiMH batteries are denser then Alkalines (by about 100g when you use 8 of them), so you may also need some additional flotation.

What we really recommend is reconfiguring your battery packs to be in parallel and using these batteries (you'll want six since three of them will fit where four standard C's would normally go). Each battery pack will end up weighing about what 4 alkalines would weigh (which is what OpenROV was designed for), and the voltage from each battery is 3.7v so with three of them in a pack, each pack gives you 11.1v which works great. Additionally, they're rechargeable (we recommend this charger), and they have a very low internal resistance (plus they're in parallel which doubles current capacity) so you wont experience the brown out issues you've described.

Hope this helps!

Eric