I have a servo controller (SSC-32) which is connected to an audio circuit (AAEF) to convert audio to a DC envelope. This latter circuit also contains an amplifier, based on the LM386, which drives a small speaker.
I am adding an Arduino Mega to the mix and I am a little confused as how to power the modules together. Both the Arduino Mega and the SSC-32 have on board 5v voltage regulators, which can be bypassed. The AAEF requires regulated 5vdc. The servos are currently powered by the SSC-32 power supply.
https://www.robotshop.com/forum/download/file.php?mode=view&id=5407&sid=7ea5ddd5a2f3d0cb14714effe2020534
It’s not an ideal arrangement. The servos probably should have their own power source. And at 5v, they are a little underpowered but are within operating range (voltage range is 4.8-6vdc). If all my servos were to operate - I’d need to supply 1.65A at a minimum (based on no load running rating) This could cause a voltage sag to the microprocessor - depending on the power supply.
My dilemma is coming up with a power distribution topology. I have a 1A power supply, or I could continue to use the PC power supply - but I don’t want to. The objective is to make this a s small and self contained as possible. I’d prefer batteries if I could get sufficient run time. At a minimum, I’d like to get rid of the bulky PC power supply.
Here is my first run at a topology. Note the comments about m/f connections are included for another reason. If you can help me see improvements, we’d be appreciative if you shared them.
https://www.robotshop.com/forum/download/file.php?mode=view&id=5408&sid=7ea5ddd5a2f3d0cb14714effe2020534
Besides, who wants to see a penguin with a power cord up its butt.
I’d recommend to use a 6V power supply to power the servos directly without needing a regulator. We have these large NiMH batteries that should last for a bit:
You can then use the SSC-32’s onboard voltage regulator to produce the 5V that’s needed for the SSC-32, the Arduino Mega, and the AAEF. Question: how much current is needed to run the AAEF?
The SSC-32 dataseet doesnt show an operating current draw. However, the onboard regulater has been derated to 250ma. The servos (separate power) will draw 1,650ma,
The MEGA draws somewhere beween 200 andd 500ma (depending on which post your read. I’m not going to a lot with the pins (the SSC32 will take the brunt of processing, so I’m going with 200ma.
I’ve never measured the current draw of the AAEF. It’s a simple circuit, rectifying an audio circuit and scaling it almost to the rail voltage; call it 4.75V.This is input to an ADC pin on an Arduino. This is done with an LT1013 Op Amp. There’s also an on board audio amp built from the datasheet of an LM386. If I get a chance to assemble the animatronic this weeked, I’ll try to measure the current draw. The mahjor hogs are the SSC-32 and the Mega, outside of the estimated 1.65A of the servos.
Here is the schematic of the AAEF:
https://www.robotshop.com/forum/download/file.php?id=5411
So all in all, I get 2,100 ma of power required. I can get a 2A power aupply and I wil try that. Of course, I’m running the predecessor design on 8A, so that may be a mistake.
I did some tests: at 9V the SSC-32 consumes 30.2 mA on VL to power the board, and at the same voltage the new SSC-32U board consumes 27.4 mA when powering the board with VS1.
If you’re servos normally use 1.6 A, we would recommend using a power supply rated for at least twice that amount.
As for the AAEF, I’d expect it to consume more than the SSC-32 or Mega since the LM386 could consume a lot of current depending on the power amplification required…
