I have bought a Romo Robot by Romotive. Unfortunately I'm having some technical issues(it does not work, at all) with it so I decided to explore the PCB a bit and see what its made of.
I understand most of the PCB and tracked down the pinouts for most of the Atmel Chip but I never had any experience with motors before. They used this motor.
Click here for a 300mm@8mp 'Hubble telescope' close-up of the PCB exposed at 15seconds, 100ISO 24f (5.5mb)
When I turn the bot on there is 3.2 V on the motors [tested the motor - & + to GND)] but testing the motor + & - and vice versa yields 0Volts. So taking the H-Brdige into account now that seems normal.
Issuing any commands the motors don't spin..(when I connect a motor direct to battery pack it spins happily away with nice torque.. ) When I issue commands the voltage is the same across the motors(apparently the signals are not loud enough or possibly the protocol changed) while attached to the PCB.. But I cannot determine if the MCU is responding at all to any commands.
Should I assume its controlled by PWM somehow? Am I correct? Most likely not.
I cannot trace which pins the motors are connected to on the Atmel either. After taking an hour to get the perfect macro shot i managed to decipher some of the tracks on the names on the IC's.
- Right motor is connected to pins 3,4
- Left motor not in picture to pins 1,2
- A on the picture indicated the tracks are connected
- ? on the picture indicated i have no idea where this track goes.. the left side does not have this
- Black "-" on picture indicated GND
- D2 as symbolised should be diodes. (KSU)(Y6)[These values are printed twice, right side up and upside down, indicating a combined diode?] I think is a
0.3W zener 18V±5%
- Q4,Q3 Indicates Transistors but research takes me to Dual 1N4148 Diodes?
- R6 indicates a resistor with a value of 102, making it 10k
- Could this whole config be the equivalent of this tutorial?
Can anyone explain to me what the red block I marked (exact same for the other side), what those SMD's are likely to be.. I tried searching for the markings on them but nothing comes up for any datasheet.(EDIT, because SMD markings are decoded differntly and many manyfactuers have the same codes for different parts, so its long game of deduction and commons sense here.. with help from awesome guys at StackElectronics!)
Here is what seems to be a bit more clear layout of the tracks and you can notice the thick tracks used for the motor pins and the thin tracks for signals. So like you suggested, there has to be a power source for this current somewhere.. I am looking at this pic and cannot really figure out where from. Obiosly it has to be switched using the paired transistors that @RussellMcMahon identified(q1,q2) and the zenners/diodes(I assume).
Romotive is an open source project.. But...
Uncomfortably there is no Source code available for the Atmel, only SDK's. My robot is dead. with
no response some response from Romo team (I know they must be extremely busy because loads of other peoples also does not work).. So I might as well make my own firmware if I knew how to drive the motors. Or at least test them with my Arduino? Or something..