B-O 328 problem


I used a baby-o 328 to control a “tyco rebound” rc car which i built a new remote for.

my problem is that it works nice when I hold it above ground in my hand,

but when its on the ground it doesn’t respond to new commands after the first one,

could it be because of friction ? the controller (driver) is not “strong” enough ?

I would appriciate some help i am stuck…

thank 's all


What kind of batteries do you have and what is their voltage? The best thing would be if you could measure the battery voltage both when everything is off and when the motors are stalled. It could be that when the motors are under some load, they draw enough current to cause the voltage to drop below 5V, causing the controller to fail.


I am using 4 AA rechargable batteries from GP (2700 mAh, ~1.3V),
you think I should use more batteries? I am now charging the batteries so they will be fuuly charged
and I will try to measure the voltage as you suggested…
thank you for the help, I will get back with an answer soon…

I tried operating the motors with 4 AA Energizer batteries of 1.5V
I measured the voltage and even with friction the voltage is above 5v (about 5.8v)
so i guess this is not the problem…
any other ideas ?


In general, using four rechargeable batteries to power your Baby Orangutan isn’t such a good idea since they will fall below 5V long before they’re fully discharged, which could cause the Baby Orangutan’s 4.3V brownout detection to kick in and reset the board as the motors introduce noise to your power rail. Can you disconnect a motor from the Baby Orangutan, connect it directy to your battery power, and measure the current while the motor is stalled?

- Ben

I measured the current and it is 0.45 A with 4x1.5v batteries
by the way the motors respond to my commands only when the brown-down detection is 2.7v and not 4.3v
I am not sure what it means…

So, with the 1.5V batteries, do you still have the same problem?

yes, the same problem. as I wrote before. for some reason when there is friction on the wheels
the program is stuck and the motors are not responding

Also, when you say you measured the voltage “with friction”, does that mean you tried completely stalling both motors at the same time while powering them? That’s going to be the case for at least a fraction of a second when your robot is first starting to accelerate, and that’s when the voltage will drop to its lowest point.


One more question - was the 0.45 A measured with the motors stalled or spinning? Is it for one motor or both together?


I connected it directly to the batteries so it was when the motor was spinning - 1 motor.
what exactly do you mean by stalled and how can I measure ?

A stalled motor is just like it sounds: it’s a powered motor that’s not allowed to spin. Apply power to the motor and then hold the case and the wheel firmly so that the motor’s output shaft cannot turn. The current the motor draws in this state is known as the stall current, and it’s a good measure of the worst-case current draw of your system.

If your free-run current is 450 mA, then the stall current could easily be 4 or 5 A, which would exceed the ratings of the motor driver on the Baby Orangutan. Please let us know what stall current you measure.

You might be able to get by with the Baby Orangutan, but you will probably have to program it to accelerate the motors gradually, and you will have to take care not to stall them out by driving into an obstacle. It sounds like the more appropriate controller for this platform would be the TReX Jr, which can be controlled via serial commands from a microcontroller (such as the Baby Orangutan) or directly connected to an RC receiver.

- Ben

when stalled (now I understand - stopped :slight_smile: ) it takes 3.6 A

thank’s for the help,

I have a question regarding the Trex Jr, from the TReX Jr RC/serial input signal connections
it shows that both tx and rx pins are connected, is the rx to the microcontroller necesery ?
(becase I use it for my remote)

It really depends on what features you want to use. If you don’t connect the TReX Jr’s transmit line to your MCU’s receive line, you won’t be able to get feedback from the motor controller, but you can still send it motor commands. The TReX can even work without any connections to a microcontroller if you run it in RC or analog mode and make the appropriate RC or analog connections to the five input channels.

- Ben