Homemade power board

Control Boards, Controllers, Tethers, Ect.
rossrov
Posts: 383
Joined: Feb 28th, 2013, 5:01 pm
Location: Australia

Re: Homemade power board

Post by rossrov »

Chuck, how did your own ESC go? In answer to your earlier post, my logic is probably the same as yours.
Driving a relay and FET from your own code:
1. Gives you the ability to tailor the control characteristics. Hobby ESCs are not designed for underwater ROVs, though some adapt well depending on the task.
2. For those wanting to learn more about electronics principles, design and programming, then you will achieve this by building your own, and get the satisfaction of knowing you designed and built the ESC yourself.
3. You can choose locally available components, so no need to wait for the HobbyKing delivery!
4. The only negatives I can think of are the greater port count, and minor extra work in programming. This is with respect to brushed, brushless alot more complex.

Ross
CLYON
Posts: 35
Joined: Dec 2nd, 2012, 8:52 am

Re: Homemade power board

Post by CLYON »

I ended up using Logic Level IRL540 MOSFETS. They are plenty for the pump motors. I am using 5 VDC coil relays to handle the reverse driven by a ULN2003. I have a 5VDC regulator to drop the 11.2 VDC from my battery to 5 VDC. I wanted to have everything at 5VDC because I thought once the battery started to drop, I wanted to make sure the relays didn't start to act up, VS a 12 VDC relay. I may actually raise the 5 VDC to 6VDC because there is a drop across the transistor in the 2003 and only about 4 VDC is actually at the relay. The port count is 4 for the MOSFET's, 4 for the relays, and 1 for a voltage monitor, so yea it adds up. The board is hand wired and I can change anything I don't like pretty easy. I would encourage anyone getting started in electronics to go this way because it is a lot of fun trying to figure how all this works. When you figure out, that design that looked good on paper wont work, its easy to change. The programing is going to be a challenge because that is the part I am not familiar with. I did buy a couple of books, one is Arduino Cookbook. It has recipes for all kinds of situations, like driving a motor, reading sensors, etc. I did some programing back in the day, but not like the Arduino. I did want to ask if anyone knew how to change the PWM frequency. I wanted to see if it would get rid of some of the motor squeal.

Chuck
rossrov
Posts: 383
Joined: Feb 28th, 2013, 5:01 pm
Location: Australia

Re: Homemade power board

Post by rossrov »

Sounds good, and good idea with the 5V relay coil. Assuming you're using Arduino, I cannot help with the PWM frequency specifically - have not done any Arduino myself. I think that it would be possible to change the library code easy enough. Someone else on the forum should be able to answer this. Otherwise write your own

Same stuff different bucket: In my code I'm using timer 0 (Atmel - same micros as Arduino) . When the timer clicks over an interrupt is generated. The interrupt increments a variable in the interrupt subroutine (function), and when the variable equals the desired "on" time variable, received from the serial port etc, the port attached to the motor/servo/light goes low. When the variable reaches a higher count, it resets to zero, sets the port high and the process repeats
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