POWERED FILTER CAROUSEL

Some time ago I made a filter carousel that was hand operated by a knob.This was for tri-filter colour imageing.Having obtained a small 200 steps per rev stepping motor I realised how easy it was to replace the knob with the motor.In the original hardware design location of the filters was via a set of holes drilled in the rotary filter mounting plate of the carousel.These lined up with matching holes in the carousel case.This meant that for a limit switch for any control electronics for the motor could be implemented using an infra read diode light emitter and an infra red diode receiver put into the holes in the carousel case.The infra red source would only be switched on during the powered transit of the motor to another filter then switched off to stop floodlighting the inside of the carousel.The same driver software that I used to drive the Takahashi FS102 focusser and the VC200 focusser would do the job with a simple addition of a pair of Cmos nand gates as a bistable switch in the hardware circuit.The method was such that a push button or a blip from the parallel port of a PC could flip the bistable over to start up the motor.This also powers up the infra red source by switching it on via a transistor switch.When the holes line up and the light shines through to the infra red receiver diode this causes the bistable to flip over into the other state and turn the motor off.This is the circuit used to power the motor.It is more advanced than the other circuit used to power the focusser units in that it uses switching FET transistors that mate to a pic output port directly This was done to shrink down the size of the printed circuit board that fits in the black box above the motor assembly.The only thing missing from this circuit is the 5 volt regulator ,the circuit is powered from a single 12 volt 7 ampere hour lead acid battery as I use for driving most things I run outside for safety purposes standing on wet ground operating telescopes and such.My pier power supplies are solar power charged in the summer into these type of batteries.

This is the inside of the carousel....

Other modifications were needed to modernise it so I replaced the means to which it is connected to cameras with a standard that all of my cameras use.This is the 2 inch diameter 25 tpi thread that Meade uses on its telescopes.Finally I wrote a visual basic program to represent the filters in use and to flip the parallel port of the PC for 200milliseconds.As there is no positional feedback this has to be manually set to the correct filter before start.If the PC port is not used a simple push button will suffice.

This is the top of the assembly...

This is an assembled view.The meade filter slider is still used to load other filters in the light path if necessary in conjunction with the carousel.The red cap covers the board that holds the 5pin mini din socket connector for the control cable and power.The small board at the bottom holds the switching transistor for the infra red diode source and the diode itself.

The infra red receiving diode is on the other side on a small board.