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DIY Radio Popper building blocks…

In perusing the web, I stumbled upon an interesting blog posting where an RF remote flash trigger was modified to send the Nikon CLS flash pulses to create DIY Radio Popper equivalents. That blog posting points to several other related postings. All very interesting… [Radio Poppers are extend the range of Nikon’s CLS system to non-line of sight using a radio link.]

After mulling it over for a while, I decided rather than purchase a boxed up pair of RF modules to modify, I would just order a bare set of RF data link modules, the phototransistors, and IR LEDs. The first pair of RF modules were a huge disappointment because there is too much chatter on the receiver end with no valid transmission, making them useless. A new pair was ordered with a better receiver module but it has not yet been received.

In the mean while, I wired up one of the phototransistors to see how well I could capture the Nikon CLS pulse train. I lifted the basic scheme from here, copying the high pass filter which filters out the contribution from ambient light. I wired it up thusly:

The resistor values are different than in the other posting I found because I did not have a full box of resistor and capacitors to pull from; I had to use what was on hand. Here is a photo of the breadboarded setup:

Here is a scope trace of part of the Nikon CLS pulse train measured at points A and B in the schematic above:

The yellow trace is from point A, the blue trace is from point B. The 330 Ohm resistor, R1, does very well at keeping the ambient office lights from contributing much to the signal in the yellow trace. The ground level in the blue trace dips below zero with successive pulses. The output at point A is probably sufficiently clean to drive the transmitter module.

The new receiver module should have an RX3310A superheterodyne receiver chip on it. It looks like the module set was designed to operate up to 4800 baud, so I suspect that the timing caps on the receiver module may need to be changed to better capture the pulses from the CLS train, since they’re flashing at about 8kHz.

More to come after the new RF link module set comes…

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Posted in diy by david on November 3rd, 2011 at 4:26 pm.

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