Monday, 21 July 2014

Playing around with Jenny

Jenny, like many of us, takes a little bit of caressing to really get going, and Julie doesnt mind me playing around with her. Of course, Jenny, or 'Genny', is short for generator.

This is the machine I picked up at the rally. After Sam and I had enjoyed our morning of Canadian canoeing, and a fried chicken lunch, we headed to ASK to pick up some two stroke oil for her. She needed a while for the oil and fuel to work into her, but soon she was throbbing away. She does like a little squirt of carburettor cleaner/easy-start to help get her going, and she runs a bit lean, so likes just a touch of choke to keep her from 'hunting', but other than that she works quite well.

She's shown above feeding a small 7A 13.8v linear PSU (it does slightly over volts anyway). 
The blocking diode needed to allow parallel battery operation was lifted from an old PSU card, I think from a transposer. Its a dial diode, each leg rated 15A. It was one of a half dozen semiconductors all mounted on the same block of aluminium, so I also took that ali block to mount it on.

A pair of lengths of my heavy duty DC cable provide the connections to the diode. A layer of tape, and then liberal coatings of liquid insulation, sealed and insulated the +Ve rail.

A small piece of heatshrink tubing, pumped full of hot melt glue, seals the -Ve rail through connection. The whole assembly was then wrapped in 3M PVC electrical tape. The red smudge isnt, for once, my own blood (I managed to save cutting myself for later!) but is actually tamper evident varnish, used to seal the thread on the bolt.

By setting the PSU feeding into the diode such that the output voltage at the diodes cathode is 13.6V, this will allow the big 38Ahr SLAB to be charged and act as a reservoir for the peak current demanded by the radios. An added bonus of this scheme is that the generator can be stopped for refueling without having to stop radio operations.

Ive managed to get a bit further with the WiFi repeater, but need to do a proper air test soon. Still to do is making up the datamode lead for the Yaesu, the 6-pin miniDIN plug I have isnt wired properly. Being a sealed plug, its not easy to change, so ive ordered a plug. I can probably get away with the old plug as a test until the new one arrives.

No comments: