Hi Terry
Yes, thanks, I have not got any fuse in the circuit at the moment, it is still very much a lash together affair across the bench job at the moment.
My plans are to try and incorporate the speed adjust/control, together with the 555 PWM from the first circuit with the Mosfet circuit, from the second schematic I posted, to control the output .
I will be using a 317T regulator to set the max supply voltage to about 14v, that stabilised supply will supply the variable control circuit and Mosfet output control.
I will also wire in the transformers second 12v winding to help improve the transformer regulation. The transformer is an old RS 0 - 12, 0 - 12, claimed to be 2A per winding, but it does get warm after being left on occidentally with no load for a few hours. The rectifier is a 6A bridge and smoothing is 4700uF.
I will use a 7805 to set the supply for the 555, if that is to low to drive the Mosfet then I will use another 317T to adjust the voltage for the 555 to the required level.
I prefer the 555 circuit in the first diagram, as it describes how to set the mid frequency of the pulses. I have read that Hornby train motors don't like the PWM mid frequency to be too high.
thanks
Mike
Yes, thanks, I have not got any fuse in the circuit at the moment, it is still very much a lash together affair across the bench job at the moment.
My plans are to try and incorporate the speed adjust/control, together with the 555 PWM from the first circuit with the Mosfet circuit, from the second schematic I posted, to control the output .
I will be using a 317T regulator to set the max supply voltage to about 14v, that stabilised supply will supply the variable control circuit and Mosfet output control.
I will also wire in the transformers second 12v winding to help improve the transformer regulation. The transformer is an old RS 0 - 12, 0 - 12, claimed to be 2A per winding, but it does get warm after being left on occidentally with no load for a few hours. The rectifier is a 6A bridge and smoothing is 4700uF.
I will use a 7805 to set the supply for the 555, if that is to low to drive the Mosfet then I will use another 317T to adjust the voltage for the 555 to the required level.
I prefer the 555 circuit in the first diagram, as it describes how to set the mid frequency of the pulses. I have read that Hornby train motors don't like the PWM mid frequency to be too high.
thanks
Mike
