Making our Meadow Blog

motors

Or what about having 2 pulleys
in the motor? The line wouldn't get tangled? Maybe need some better way to
separate the 2 lines as they wind on/off? Could even make the pulleys?

mmmm

C



Even better yet is there some sort of gear configuration that
would do it, I wonder?
 
 
Although this would need to be precise and therefore
expensive so probably more expensive than just another motor plus more
difficult to achieve and get right. It does seem like a more elegant solution
though… Having two cables under tension should help to provide a brake,
as long as they remain in sync.

The two motor idea sounds very scalable to me. Also it would be pretty simple
to set up I think. Whatever you use will be exposed to the elements and maybe a
rubber timing belt would crack/ perish? 2 motors wired CC and CCW would be
quite a nice solution i think!

Colin

Now onto
the transmission… this looks like quite a good site (http://openmoco.org/node/243)
and seems to suggest timing belts and pulleys (got some prices from RSS). But I
don’t know how well it will work over 3m. The longest I could find was
2.8m (http://uk.rs-online.com/web/search/searchBrowseAction.html?method=getProduct&R=4750759),
I assume you need twice the length of the span required. I suppose you can join
them together with additional pulleys but I guess that it becomes quite
inefficient?
I found a very simple method using a fishing line and a tap wrench chuck (no
pulleys or gearing at all, seemed to work fine – all the
‘evidence’ on you tube) but it would seem to be a good start. I do
wonder whether it is simplest to have a weight on the end which pulls the dolly
back as the motor unwinds? Or would this put undue pressure on the motor during
the time that it is held in position?
Alternatively, could I have two motors which wind up and unwind simultaneously?

Meadowcam 2 Motor trial 1

Tested the motor Colin has lent me. I managed to get the Stepperbee + working with the power supply and Autostepper software. However when I tried the motor, although it worked, when I wired it up correctly the motor simply moved back and forth. I tried removing wires and when the B/ and B wires were removed it did work but with one of the steps skipped. It also stopped working entirely when the interval was reduced below 60ms. Undeterred I hooked the dolly up and played about. Obviously I wanted to get it zooming back and forth, but it turned too slowly and fact that it wasn't fixes down meant it just jerked about. I did manage to get it to wind up the fishing wire a little bit but then it just started spinning. The other main issue was heat; it was really very hot indeed.

Meadowcam 2

My plan has changed from using a
garden rail system to a home made dolly made from aluminium angle and skate
board wheels (see below) mounted on a 50mm x 50mm post used as a rail.
 

The trial plan is to use a short length of rail and a length of heavy duty sea fishing
line connected to a spindle. The spindle will be turned by a stepper motor a
friend is supplying controlled by a driver from a very handy online company
(http://www.pc-control.co.uk/) which can be
controlled via a PC and (when I have learnt Visual Basic…) programmed to
only operate in daylight hours and reverse when it reaches two data points. The
pictures will be taken initially by a webcam (I have one there already) just to
see if it is a worthwhile project. Eventually I will replace it with another
camera, probably a Canon Compact type (which can be programmed) although I am
looking into other options.  
 
Note that the rail is on a slight incline so the cable
pulls it up gradually and then unwinds to allow it to move back gradually. I
am proposing to have the dolly moving continuously at a very slow speed
rather than starting and stopping.

The sensor may be irrelevant, since the software which comes
with the Motorbee Controller allows quite precise control of the motor

If this works I’d like to upgrade the camera to a canon digital camera with a chdk intervalometer
script, and extend the rail and cable to either 3 or possibly 5m. I think
for the garden job I can move the PC and 240v power supply to the centre
of the rail and it would be ok if the camera battery were ground mounted
in a suitable box and connected to the dolly via a long cable (to keep the
weight down). Ideally I’d like to get this done next summer.
Eventually I would like to upgrade it again to be a fully mobile system which can
take a DSLR and can be run either continuously or stop move stop. But that
is a long way off.

I have now got a stepperbee plus (which allows a pretty hefty stepper motor to be
used) with Colin’s assistance (and one of his motors) I can test how well
it works shortly and see what sort of weight it can bear. The battery I am
currently using on the static Meadowcam is 6.25kg. I should imagine with a box,
camera and solar panel it would weigh up to 10kg!  
Another thing to consider, suggested by Phil, was the position of the camera and the
rail in relation to the sun, to avoid shadows affecting it.

Orchids round three

Just got back from a 4 hour round trip to get some more orchids from a nice chap in Lincolnshire. The woman I sat next to was right: the roads there are rubbish... Collected a green winged orchid, a couple of pyramidal orchids and two dactylorhizas I'd ordered and I treated myself to a bee orchid from his huge stock. Now to stop the slugs...