An alternative slotted opto switch.

[Steve Anderson]

I was looking for some other devices on the Farnell (UK) site when I came across this...it's a slotted opto switch that has a built in active switch/Schmitt amplifier, works from 5V up to 16V, the sensor has only 0.5mm width of area and the slot is 8mm wide. It's also only 2.13 pounds +VAT. Farnell stock code 1173622.

It should take away all that fiddling away with the pot and couples directly into the 4046. Here's how I would start out with it, if using 5V, resistors pro-rata.

Depending on the size of your sync-pulse holes you might need to run the IR LED near its maximum current by reducing the value of R1 to 270Ω/1W for 'European' temperatures at 12V, 100Ω for 5V.

Steve A.

P.S. There are some errors on the attached datasheet (how unusual), but it's no real concern if using this device for NBTV.

[Steve Anderson]

Having studied the datasheet for the above device its speed of response might be a little sluggish as shown with R2 being 2k2. I suggest reducing it to 1k which will speed up the edges of the output pulses.

However, it's worth trying at 2k2.

Steve A.