OSMC Motor Controller with BS2

Technic-R-C

Hey guys,

I am currently working on a project in which I have to interface the BS2 chip with the OSMC Motor Controller.· The OSMC motor controller is a simple H-bridge power amplifier. It does not have any on-board logic to interpret RC or other commands. However an external logic interface is required to translate command inputs into the PWM signals needed to drive the board. This increases system complexity somewhat but also increases flexibility as the OSMC board may be driven by any microcontroller or other signal source that can provide PWM and Enable logic.

In order to connect to the OSMC (10 pin), it looks like I need an external 12V 1/2 Amp Power supply and only PWM signals coming into the board to control the board.· The description of this pinout can be found in this manual on page 14-16 and is also pasted below.· I have some ideas on how to accomplish this, but I really do not want to burn my BS2 or mess it up.· I would appreciate if you guys could help me out on this one.

Thanks

Technic-R-C

Post Edited (Technic-R-C) : 5/30/2009 8:59:58 PM GMT

Franklin

www.robotpower.com/downloads/osmc3-22sch-clean.pdf

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- Stephen

Technic-R-C

Great!!!
That helps alot, im gonna test it out as soon as possible.
In the meantime I have a quick question about the power supply:
If the OSMC needs 12 V .5 Amp and I have a 12V 6 Amp Power Supply, will this burn the circuit?·
Im assuming not due to the fact that the voltage is the only factor that could burn a circuit and the amount of amperage that is needed is pulled·by the device, not·outputed by the battery, therefore it should be ok.

Thanks

Technic-R-C

Technic-R-C

Well·I got all the parts and everything is hooked up ready for testing but I am kind of hesistant about connecting the 12V 6Amp power supply to the 12V .5Amp rated OSMC motor controller.·· I'm assuming the device only pulls the necessary amount of current and not all 6 Amps.··But just to make sure, could someone provide some insight into this issue?

Technic-R-C

Franklin

You are right in your thinking.

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- Stephen

RobotWorkshop

How are you planning on connecting your power? I hope you are looking at supplying it to the BATT+ and ground. If you look closely at the OSMC board you will see that U1 is used to generate a +12V supply right on the OSMC board. You should only connect power to the BATT+ and ground. Usually this is a 12V or 24V power source made from Sealed Lead Acid or NiCad battery packs. Keep in mind that the FAN terminal at J1 come right from the battery power so it should be rated accordingly.

If you want to power the Stamp and don't have much else drawing power you can use the 12V generated by the OSMC board to power the Stamp. This is the way that some of the original controllers for the OSMC worked (like the uMOB). This way you just need a single power switch to turn on the OSMC and controller. At least that is what I used on one of my old Battlebots that used the OSMC boards.

Robert

Technic-R-C

RobotWorkshop:

Thank you for your helpful input.· At the moment i am using a 9V 300mA wall power outlet for testing purposes, however·I will definately consider regulating the OSMC's voltage and powering the Stamp through this power supply very soon.

So in general, I have to:

Pull pin 4 low to activate OSMC
Pull pin 5 and 7 high permanently during running of OSMC
Regulate 6 and 8 for direction and speed of motor

All of the·pins above (except for 4)·are pulled down using 10K resistors which are wired to the Vss ground (on the BS2) .

Pin 9 and 10 are also connected to Vss (on the BS2) to complete the circuit.

Pin 1, 2, 3 are not used.... but will be used and regulated to power the BS2 and monitor voltage

Questions:

Is power from the OSMC coming into the BS2?· It seems as though power is coming in due to the fact that pull down resistors are necessary.· Can this power input damage the BS2 (especially concerned with pin 4)?
Are my steps to connecting the OSMC to the BS2 correct above?

Problem concerning pin 4... In order to power the OSMC pin 4 has to be driven low from high.· Off course this is illogical since it is high on startup I can't forcefully make it low.· However I found this snipet in the manual

A note about DIS polarity: If you are using a motor driver other than the OSMC and it requires the DIS
line to be asserted LO (that is; motor disabled whenever DIS = 0 Volts), you will need to set the
“dis_activelo” bit in the appropriate MODE byte in the Parameter Block. This will reverse the normal,

default, polarity of the DIS signal to accommodate your driver.

It states that DIS will be reversed (pin 4) so that low = off and high = on.· However where do I find this dis_activelow bit to change these setting???

Thank you

Robert

Srry for late response, I wasn't feeling to well these past couple of weeks....



Post Edited (Technic-R-C) : 6/24/2009 3:52:05 AM GMT

Technic-R-C

Hello everyone,

I have successfully got the OSMC to work!·

To all future users of the OSMC with BS2, i'd like to let them know that my previous instructions in connecting this device to the BS2 were correct however the voltage applied to the OSMC was incorrect.· I was applying 7.2 volts but it had to be a minimum of 14 volts to funciton correctly.

Regards

Technic-R-C