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Forum Newbie
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Hi.
I have a problem here..
I have a speed controller that takes in:
PWM cable, 12V/GND
and gives:
Motor +/-
Thing is the PWM cable looks like the three cable input cable like the ones you connect to the
AnalogInput, GpioInput pins. (VCC, GND, signal).
We're using this to drive a DeWalt 12V motor that takes 6.3A when directly connected to a
7AH 12V battery.
If I were to use this with the motor, how should I connect this?
I've already tried to attempt to connect to the external h-bridge jump pins but to no avail..
PLz help! Our presentation deadline is within a week and this is the only thing that is problematic..
All the algorithm is done and all 
Thanks,
Seungjin Kim
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Forum Member
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Last Login: Wednesday, November 05, 2008 10:13 AM
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| Do you have a spec for your controller? You say PWM, but is it really a PWM that runs at 10 khz, or is it a servo type control signal? If it is a real PWM line then then you will need to hook you 12V and Ground from your battery to the controller. Then hook up a pwm line form the serializer and a ground from the serializer. You must have a common ground. Don't just use the serializers ground, you don't want 6A going through that. So your controller ground wire will look like a 'Y'. You can then use the PWM command to control it. If it is a servo type signal that runs at 50hz with a 1-2ms signal with a 1.5ms center spot, then you need to use a servo control line form the serializer and use the servo command. Follow the same wiring instructions as above for ground and power. Ringo
Ringo Davis
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Forum Newbie
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Thanks for the fast reply.
The specific speed controller is a Victor 884 from ifirobotics.com.
I have a few questions about your reply.
================================
You say I have to connect a PWM line from the serializer to the speed controller, if case 1).
Are you saying to draw one from one of the Analog pins? And make it so that the ground has two
connections - one to the PWM cable ground, another to the battery ground?(so it forms Y)
Also, I'm trying to use this under C#. What component corresponds to this setup?
Documentation states to use PWMDCMotorController object would control DC motors but
from my understanding that just controls the voltage levels(via PWM maybe?) on the two
DC voltage outputs (2 green DC outputs). If I were to connect PWM cables to the Analog Pins,
then PWMDCMotorController object won't know about it - it only allows assigning MotorId, not
AnalogPinId.
================================
Here's the spec about the PWM it uses:
"Use a standard non-shrouded PWM cable (3 wires)"
"Standard R/C Type PWM (Pulse Width Modulation)"
=>I'm guessing.. this means a real PWM line?
And the site:
http://www.ifirobotics.com/victor-884-speed-controller-robots.shtml#Specifications
Thanks in advance,
Seungjin Kim
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Forum Newbie
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Bump;;;
Please? Anyone? I really need help!
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Supreme Being
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| I'll let Ringo answer the electrical questions, but the PWMDCMotorController object in the .NET library doesn't know the difference between a motor connected to the green motor ports (which are connected to the onboard h-bridges), and one connected to an external h-bridge via the h-bridge pins. The analog inputs have absolutely nothing to do with controlling h-bridges. The Serializer User Guide shows you which of the pins to connect to external h-bridges, and which traces to cut. Basically all you're doing by cutting the traces is severing the electrical connections to the onboard h-bridges, and then using jumper wires to run those connections to external h-bridges (via the h-bridge pins list in the User Guide). If you have things wire so that you're somehow using the analog pins, you're probably going to fry something. Nowhere in the User documentation do we mention utilizing the analog pins for PWM/H-Bridge interfacing. So, be careful! Best Regards!
Jason Summerour
President,
Summerour Robotics Corporation
Microsoft MVP
www.roboticsconnection.com
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| The IFR docs really don't say, so I'm assuming that it is an RC type PWM since it mentions using standard RC type connectors. So it has nothing to do with the h-bridge. Connect it up to a servo pin for your signal, and use the servo commands to control the motor. The digital ports on the serializer have 3 pins, gnd, 5V, and signal. Use the signal pin to go the the victor, and make sure to connect up a ground as well, but make sure you have a good ground and 12V from your battery to the victor. From a previous post I think you understand what I mean by the grounding, but if you are not sure, then let me know and I'll try to draw something up. Check the serializer manual on which pins work for servos. Ringo
Ringo Davis
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Supreme Being
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| Oh! He's trying to drive his controller via servo PWM! Ahh...okay... Yes, there are 6 servo ports on the Serializer (in the digital I/O bank), which you should be able to leverage. Best Regards!
Jason Summerour
President,
Summerour Robotics Corporation
Microsoft MVP
www.roboticsconnection.com
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Forum Newbie
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Thanks guys for the in-depth replies!!
I'll try the solutions as soon as I can(i.e. coming weekend).
As for the grounding, I understood it as this:
GND(battery) ==============================
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||======PWM's GND pin in Victor
||
GND(from Serializer's Servo GPIO Jumper pin)=======
Is my understanding correct?
Thanks again,
Seungjin
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