I have been doing a lot of researching ever since Christmas when I got the Arduino Uno. Anyways, I want to build a 4 leg spider robot using 2 Arduino's. I had a lot of problems on coming up with how to do it, and I think I got it. What I want to be answered is this question, is my circuit good to go and will not fry anything? Anyways, I needed 12 servos. Only 6 pins on 1 Arduino has PWM. So I thought to use 2 Arduino's to communicate through the HC-06 blue-tooth. Power was another problem. I discovered that double AA batteries have an impressive 7 amps on my multi-meter. However, to much for the Arduino. That is why it is only supplying servos and not going directly to the Arduino. A 9v will do that. Anyways, I can't give you guys the schematic as it is to big of a file. However, I will explain the circuit in words. One Arduino is master and the other is slave. These steps go to both master and slave unless stated.
6 servos on master and 6 on slave. Power is going to 4 double AA batteries in series. This supply is not connected to the board except the ground wire. This is a battery holder with switch already on it. All PWM pin's are in use for servos.
9 volt battery going to the Vin pin. I will incorporate a switch.
Fan with positive and negative only. Positive goes to the 9 volt battery. Ground goes to ground pin on Arduino.
Bluetooth module with VCC going to 3.3v pin. Ground to ground pin. TXD going to the RX pin. RXD going to TX pin.
For master Uno only. Distance sensor with Trig going to A5 pin and echo to A4 pin. Ground going to ground pin. VCC going to 5v pin.
2 led's in circuit with 220 ohm resistor. I will use pin 4 and 2. Ground goes to ground pin.
That is the setup. I am in college where soldering is banned. So I am including a fan, like you saw, to cool down the breadboard. Let me know if you think that will work. I could not find a good schematic online for this robot, so I made one. Please let me know if you have any questions. Anyways, please tell me if there are any flaws and thank you so much for your time and effort.
Edit 1: @gilhad I did not know about I2C, if that is easier than blue-tooth, then I will get that. Thanks for that input. This way I don't have to use 2 blue-tooth modules. Most of the robot is running in series, not parrel.
Also, I said 4 AA batteries and not 2. If I had 2 in series, then that is 3v only, so that is why I am going for 4 in series for a total of 6v, with amps being the same as with one battery. This will supply 7 Amps. I tested it with my multi-meter. The servo motors are going to need 1 amp of power at max. I have 7. I will probably be using 4 servos at one time. So that is 4 amps. It will run for about an hour. That is fine by me. This 4 AA battery is not connected to the arduino. There are 2 power sources per arduino. The other one is a single 9v battery, that one is going directly to the arduino, the Vin pin to be clear. If it is going to reset, could I do something in the programming to account for that like a time delay that is short?
I do not want to mess with my breadboards, that is why I am using a fan to cool them. Will that work?
The power source will not be moving all the servos at once, sorry that I did not include that.
I guess I did not want to get a mega because I have 3 Uno's already, but I see they're pretty cheap online. I will ponder this idea of yours. I looked at my schematic and determine this would eliminate the 2 blue-tooth modules, 1 power source, 1 fan, and 2 leds along with their resistor. I think it would also eliminate an extra switch. Programming would be easier to because I don't have to worry about blue-tooth communication. I had no idea what to do for that one. So maybe I will get a Arduino mega.
The reason I am not using RC battery is because they're kinda heavy and SG90 servos are kinda small. I was worried about torque. Li-ion is not to heavy, but I was worried about power. The ones you gave me though, look like that might work. There is 2 problems though. First, I can't use 2 of these batteries in series because that is 7.4 volts when the servos I am using is at max 7.2 volts. I would have to reduce voltage somehow, I have no idea how to wire that into the circuit. Problem 2 is that if I wire is parrel, that is 6 amps, which is fine, but only 3.7 volts. The motors can run on that, but that is on the low end. Will torque be less?
About the third paragraph, there is limits on the amount of current an Arduino can take. I looked them up. It is about 2 amps for the Vin pin I think or that might be the DC jack, one of the two.
I am using 2 Arduino, so that is why the blue-tooth was necessary. However, if I go with the mega, it will eliminate both of them. I forgot to mention for the distance sensor, I am using ultra sonic one. That is my fault for not mentioning that.
The reason I need 12 servos is because I am using 4 servos at the base, one for each leg to control direction of leg for steering. Then I have 4 legs, each using 2 servo motors to make the leg kick out and in. So 4 + 2(4)=12.
Yes, I would be using, if 2 Arduino, wireless communications, that is why the blue-tooth module. About the schematics, the picture is too big, so that is why I can't upload it. So sorry about that. I did try, believe me.