Internet PLC Forum
General => Technical support => Topic started by: kenobe on September 30, 2008, 01:34:55 AM
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Hi
I am using the T100MD 888 trying to run a DC motor in forword and reverse directions using the pwm function.
But I can not figure out how to do it
How should I connect the hardware?
now I can only control one direction but not bothpls help!
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In order to run the motor bi-directionally you need a bi-polar driver which is not possible on the PLC's built-in NPN only output. You need to build a "H-bridge" so that the current can flow in either direction. The H-bridge could be built using an external relay with dual-pole, dual-throw contacts and you wire it in such a way that a single PLC output can select the direction that the current would flow through the load in the H-bridge. In order to use the NPN PWM outputs you connect the ground return path of the H-bridge to the PLC's output instead of to "0V" directly, and in that case the current that flows through the load in either direction will be chopped wave (PWM) since the PWM out driver would be controlling the current path being returned to 0V terminal.
The following website has good explanations of how a H-bridge works:
http://www.dprg.org/tutorials/1998-04a/
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Hi
Your reply is very helpful, I sincerely thank you for that.
my problem now looks like resulting to finding a high current ie:10A H-bridge module.
thanks! Thanks!