Optical Encoder Resolution Reducer

[Algar_emi]

I need to reduce the resolution of an optical encoder. The actual resolution is of 256CPR and I need around 100CPR. I know that using IC we can increase the encoder resolution. Does anyone knows how to reduce it?

I tried to use a divider by two using a flip-flop on each phases of the encoder (256/2=128CPR) but got mixed results. Some time the decoding circuit is reading correctly the encoder, sometime it is not. The encoder response sometime goes up with a CW motion. sometime it is the other way around. I suspect that the correct phases of both outputs A & B is mixed up by the divider.

I knows that it can be done, see the EDIVIDE at www.usdigital.com but I'm looking at a cheapest DIY alternative...
See http://www.usdigital.com/products/edivide/

Thanks in advance.

SB