Re: [CAD_CAM_EDM_DRO] Re: low voltage contorl circuit

On Tue, 27 May 2003 00:25:03 -0000, you wrote:

>--- In CAD_CAM_EDM_DRO@yahoogroups.com, Harvey White <madyn@i...>
>wrote:
>> On Mon, 26 May 2003 18:08:48 -0000, you wrote:
>>
>> >Hi,
>> >
>> >has anyone made the low voltage regulator from the
>mosfet/transistor
>> >design in the files section ?
>> >
>> >/CIRCUITS/HIGHINPUTVOLTAGEREGULATOR.pdf
>> >
>> >I need to get 5 VDC from the secondary of a 48V transformer, may
>need
>> >to use the center tap to get 24VAC for this.
>> >
>> >just wanted to know how noisy this DC voltage will be.
>> >
>> >or, if anyone has a circuit to drop higher voltage to 5VDC without
>> >adding huge heat sinks to the voltage regulator.
>>
>> One idea would be to go get either a small regulated 5 volt supply
>and
>> use it independently, or get a cheap 9 volt dc supply and run it
>> through a 5 volt 7805 regulator.
>>
>> In a CNC setup, this would give you good isolation between the
>> voltages and keep the switching noise from the chopper drives
>down. I
>> plan to do much the same with an isolated board driver (CNC setup)
>> being driven from a printer port. I will have a separate power
>supply
>> for some of the logic circuits, which will be completely isolated.
>>
>> Harvey
>>
>>
>> >
>> >Dave
>
>Hi Harvey,
>
>I am planning on using 5V logic for the EDM and it seems the MOSFETs
>for the EDM and the circuit driving them need to have a common
>ground. I was hoping to run the 5V off the main power source and
>that way keep some of the problems to a minium.
>
>I thought that using a seperate power source does not offer very much
>isolation when you need to tie the grounds together.

Isolation of ground noise and common mode noise on the signals, nope.

Isolation of noise on the stepper supply from the logic supply, yes.

Your option if you want a completely floating ground is to use optical
isolators, but then you need a gate supply for the FETS.

Harvey

>
>Dave
>
>
>