TITLE: Charging the laser scanner off a generator
DATE: 2020-02-25
AUTHOR: John L. Godlee
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In the past my fieldwork with the laser scanner has been in a place
with a permanent large diesel generator, so I could just hook in
the battery charger for the laser scanner as I would on a normal
house circuit. For this fieldwork however, I will be moving around
more and I will be based in small villages with no electricity
supply. In order to power my equipment I have had to invest in a
generator, which has demanded a lot of learning about generator
maintenance and electrical circuits.
We used a portable generator for a single day during the last
fieldwork and it blew up the battery charger, meaning I had to ship
a new one from the UK. The generator was a little one which you
would find more commonly on a building site, it wasn't really
designed for powering sensitive equipment like computers. When I
got back the to UK and interrogated the GEF people, they said that
normal generators like the one I had used often don't provide a
constant power output, that is, the sine wave of AC current isn't
that well modulated, it jumps around all over and can cause fuses
to blow. In my case I was unfortunate because the spike had somehow
jumped the plug fuse and blown up something internal to the machine
which couldn't be easily repaired. The answer was to buy an
"inverter generator", which uses a micro-computer to electronically
modulate the sine wave of power output, making the output much more
constant.
I couldn't afford to bring a generator on the plane, though it
would have been a lot simpler and saved me a lot of anxiety if I
could have brought one on the plane, as I would have been able to
test it before I arrived and be guaranteed of its compatibility
with the scanning equipment. I opted instead to buy one in Dar es
Salaam prior to my bus journey down to Kilwa Masoko.
A driver and I first stopped at a South African hardware store in a
big mall called Mlimani City, but they only had conventional
generators. Next we went into the centre of the city to India
Street where there are a bunch of small hardware shops, many of
which have loads of generators. Still, finding an inverter
generator was pretty difficult. Of the 10 or so shops we went in
which had normal generators, only 2 had an inverter generator. I
opted in the end for a Honda eu20i because I had already seen them
online when I was researching this back in the UK, the other option
was a non-descript Chinese generator, which seemed suspect. None of
the generators were the ideal 1.5 KW output, the eu20i is a 2 KW
output, meaning its a bit more bulky than I would like, but at
least I got one.
The next issue was hooking it up to my equipment. I got some cable
and assorted sockets thrown into my purchase as a bargain, as the
socket outlet on the generator was for a US/Japan 2 flat-pin plug.
I had been hoping for a UK type plug because that's what is used
commonly in Tanzania. Maybe I should have pushed harder for a
proper adaptor or looked for a different generator.
I took apart my 3 round-pin to UK socket adaptor, leaving only the
UK female part, and wired it up via some spare flex to a US/Japan
2-flat pin plug which ift the adaptor. The issue was providing a
fuse somewhere along the circuit, so I will always have to run the
generator off my multi-socket, which has 4 thermal fuses inside it,
one for each socket.
I tested out the hacked together setup and amazingly it worked. I
also learned how to top up the oil and got some 4-stroke oil from a
"Lubricants" store. I am still slightly worried about the cable's
performance in the rain. I will try to keep it under cover while
using it.
