Why Isn’t My Dual 555 Timer With Inverted Signal Working for H-Bridge Circuit?

A user attempted to drive an H-bridge circuit using a dual 555 timer configuration, where one 555 timer generates a PWM signal and the other provides an inverted PWM signal. The circuit did not function as expected. Key issues identified include the use of optocouplers with thyristor outputs, which are unsuitable for driving MOSFET-based H-bridges; transistor-output optocouplers are recommended instead. The potentiometer in the circuit adjusts duty cycle rather than frequency, and maintaining a 50% duty cycle on both PWM signals will prevent motor movement. To vary frequency while keeping duty cycle constant, changing the timing capacitor value (e.g., the 10nF capacitor) is suggested. Additional diagnostic advice includes capturing oscilloscope waveforms at the 555 timer output pins and motor terminals to verify signal integrity. More detailed circuit information is needed for precise troubleshooting.
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