Red Power Controller - Low side FET
Verfasst: 01 Mai 2018, 04:54
With reference to the ft Power Controller, that has 9V DC Out and adjustable Motor output.
For the motor output, it uses a Field Effect Transistor (FET) that is connected to the ground reference, so as you rotate the dial, the ground reference shifts up and down. In other words the voltage reference is actually the plus 9V rail. So if you want 5volts output, you get 4volts on ground.
This is poor engineering to me, I would never design it like that. Its fine for an isolated motor, but now its very tricky to use it in other circuits. You will end up damaging older vintage ft if you use it the same way as the older transformer base power supply.
I understand this is a super cheap electronics design, it uses a very common 555 timer to generate a PWM that feed into the low side FET. You can't get cheaper. But gee, why not use a high side FET and adjust the +ve rail instead?
Some better output filtering would good too.
Has anyone modified the board to correct this?
Thanks
Michael
For the motor output, it uses a Field Effect Transistor (FET) that is connected to the ground reference, so as you rotate the dial, the ground reference shifts up and down. In other words the voltage reference is actually the plus 9V rail. So if you want 5volts output, you get 4volts on ground.
This is poor engineering to me, I would never design it like that. Its fine for an isolated motor, but now its very tricky to use it in other circuits. You will end up damaging older vintage ft if you use it the same way as the older transformer base power supply.
I understand this is a super cheap electronics design, it uses a very common 555 timer to generate a PWM that feed into the low side FET. You can't get cheaper. But gee, why not use a high side FET and adjust the +ve rail instead?
Some better output filtering would good too.
Has anyone modified the board to correct this?
Thanks
Michael