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LX90 First Light (longish)



 
 
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  #31  
Old April 27th 04, 07:22 PM
Colin Dawson
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"Chris Taylor" wrote in message
news:6unjc.10$96.0@newsfe1-win...
Hi Colin

I own 2 GOTO scopes and both have their own 1.2Ah batteries. I've not
noticed any difference between the beginning of the evenings battery's
performance (slewing speed or sound), or the end of the session on either

of
them. I do spend more time tracking with the LX90 given that the LPI get's
used. Nonetheless, I've not had the battery go flat, or appear to be
labouring on the LX yet and I've spent from 8pm to 2am observing. The C
Cells are an expensive way to do things so I bought the Lead Acid before
they could go flat. On the Celestron GOTO the batteries (AA's!) used to go
flat in a few hours and were a waste of time and money; lesson learned.


hmm, you're lucky. I think it's partly because I'm such a pickky little
blank (insert bad word of your own choice)
but I've noticed that about 1/2 way through the session my scope starts to
sound a less perky than at the beginning of the session. It doesn't seem
to affect the performance though, but I'm definatly not making it up.

I've just checked the Duracell web site, and they rekon that the LR14's will
work for 11 hours at 0.5 amp current.


There's also no reason not to get a 7.2AH and I'd have probably bought one
if the closest shop i could find with a solution (B&Q) had sold them. The
other alternative was a 45 Minute journey to Maplin, or a few day wait for
an internet purchase to arrive.


From the information that you've provided, I think that the only need to a
bigger battery it to help power more toys.
Can't have too many toys.

Regards

Colin Dawson
www.cjdawson.com


  #32  
Old April 27th 04, 07:22 PM
Colin Dawson
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"Chris Taylor" wrote in message
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"""I can't think of any reason why they can't add a 1n4007 diode."""

We used to call this the 'idiot diode', placed in parallel with the input,
and a fuse in series with the input, it would short, and blow the fuse

when
some idiot reveresed the polarity...


Ouch, that could be a really expensive lesson. Mind you - you'd only do it
once or twice then learn WHY the fuse keeps going POP :-)

Regards

Colin Dawson
www.cjdawson.com


  #33  
Old April 27th 04, 07:22 PM
Colin Dawson
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I can't think of any reason why they can't add a 1n4007 diode. It's way
overratted for the needs of the scope and will stop any polarity

problems
dead.


No, it's UNDER-rated! It is a 1 Amp diode and your earlier figures
indicate over 2 Amps when 2 axis slewing.


Oh yeah, no problem. I've seen diodes that can take huge amount of power.

The only reason why they didn't (that I can think of) is that there
is a 0.2 (I think it's 0.2 anyway) voltage drop over the diode which

might
affect the performance of the scope.


The forward voltage drop will be more like 0.8volts at rated current.


That's worse that I thought, suppose I should have checked the figures.
That'll go some way to explaining why they didn't bother - loosing .8 of a
volt when running on 'C' Cells will make the batteries appear drained really
quickly (like it's not a problem anyway) the scope needs every bit of the
12V.


Basically No reason at all.


Other than those, no. 8¬)

A better solution is to wire a 12VDC relay in series with a small diode
(the 1n4007 above would do) and place that arrangement across the
supplies' input wires, checking that the relay actuates when the red
wire is attached to the +ve pole of the battery.

Wire up the relay contacts to connect the supply to the load through the
contacts which close when the relay is energised - these are the n.o
(normally open) contacts.


Yep. That'll do it.

Regards

Colin Dawson
www.cjdawson.com


  #34  
Old April 27th 04, 07:22 PM
Colin Dawson
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"Andrew Cockburn" wrote in message
-service-com...
Very nice !

One question ... on PowerIndicator.jpg what is vr1 for ? I assume it is
preset for calibration, so do you just set that so the led's read full
just after a charge ?


As I said, the circuit was is a modified version of one that I found on the
net. Here's some more details about the circuit itself....

Connect an input voltage of 12.65 volt between the positive and negative
poles and adjust the 10K trimmer potentiometer (That's vr1)
until Led 10 lights up. Lower the voltage and in sequence all other Led's
will light up. Check that Led 1 lights up
at approximately 11.89 volts.


At 12.65 volt and higher the battery is fully charged, and at 11.89 is
considered 'empty'.
The green Led's indicate that the battery capacity is more than 50%, the
yellow Led's indicate a capacity of 30% - 50%
and the red Led's less that 30%.

The original circuit for this was on
http://www.uoguelph.ca/~antoon/circ/batmon12.htm so no pont re-inventing
the wheel. The modifiction that I made to it was to add the 5K6 resister
to Pin1 and V+ This then uses up some current that is drawn through this
pin whenever the signal is about the voltage required to light LED2 and
above. Basically it allows the circuit to work in both dot and bar mode,
better than the original circuit. I'm not sure, but I think this may not be
required if one of those bar graph displays is used. I decided that I
wanted 10 3mm LED's to spread the scale out a bit.


Also, if I could persuade you to share your PCB design when you are
ready that would be great !


Here's the link to my PCB Layout.

http://www.cjdawson76.btinternet.co....dicatorPCB.jpg

Print it so that the outline is 100mm * 75mm. This will give the correct
proportions on the print. This layout is meant to be printed onto
transparency for Photo-etching.

To complete the job, lay this ink side up onto a glass sheet. Place the
photo-sensetive side onto the transparency, so that the ink touchs the photo
film. This will ensure the best possible image. I won't go into details
about photo etching, for anyone not familer with photo-etch techniques,
that's why it appears to be reversed.

If you use the circuit diagram
http://www.cjdawson76.btinternet.co....rIndicator.jpg you
should be able to work out where all the components are supposed to end up.


As per your and Chris' advice, I'll get the car-starter to keep me
going, then I can spend some time puttting together the whole power
supply, and dew heater. What kind of box are you planning on using ? I
was thinking of using a largish plastic toolbox as I am crap at woodwork

....

A Car starter will keep you going to quite a while. You might even decide
not to try to *improve* on it. Another alternative that I thought about was
to have the Dewheater and scope power in one box, then a lead that connects
to the Jumpstarter.

As for the box, I'm also crap a woodwork, but I just can't seem to find a
box that even comes close to fitting my needs. So I've decided to bite the
bullet and build one from wood. It's taking alot of thinking about, but
it'll be worth it in the end.

Regards

Colin Dawson
www.cjdawson.com


  #35  
Old April 28th 04, 08:14 AM
Andrew Cockburn
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Ho Colin,


As I said, the circuit was is a modified version of one that I found on the
net. Here's some more details about the circuit itself....
...

Thanks for the detail :-)
Also, if I could persuade you to share your PCB design when you are
ready that would be great !



Here's the link to my PCB Layout.

http://www.cjdawson76.btinternet.co....dicatorPCB.jpg

...

I haven't done any electronics since I were a lad (this is a great
reason to get back intot it!) - In those days I made PCBs using
transfers and etch resist pens. Is the photo-etching expensive to get
setup ? I bet the results are a lot better .. I'll do a little surfing
and see I think.

A Car starter will keep you going to quite a while. You might even decide
not to try to *improve* on it. Another alternative that I thought about was
to have the Dewheater and scope power in one box, then a lead that connects
to the Jumpstarter.

At the very least it removes the urgency and lets me think about it in
more detail.
In all my vast experience of using the scope (1 night !) I haven't dewed
up yet, but
as soon as I do I know I'll wish I had the dew-heater handy so I'll
probably plug on
and get it going anyway. which means I also need to do the power thingy.

As for the box, I'm also crap a woodwork, but I just can't seem to find a
box that even comes close to fitting my needs. So I've decided to bite the
bullet and build one from wood. It's taking alot of thinking about, but
it'll be worth it in the end.

Good luck with that ! If I can't find the right kind of toolbox I may be
forced to do the same. I've got a mate who could help though, so maybe
for the price of a few beers I can get one together.

Regards,

Andrew

Regards

Colin Dawson
www.cjdawson.com


  #36  
Old April 28th 04, 08:17 AM
Andrew Cockburn
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Colin Dawson wrote:


I just did a quick new search and found a cable (from IXOS) that works for
both car and plane... Looks like you might be in luck. It would be worth
digging it out, and typing the model number into Google, hopefully you'll
get some more info.

I dug it out and it takes 13.8v in - which probably means it works on
12v. Its worth a try before I fork out on a maplin or eBay one.

Andrew

Regards

Colin Dawson
www.cjdawson.com


  #37  
Old April 28th 04, 09:51 AM
Tim Auton
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Andrew Cockburn wrote:
Ho Colin,

[snip]
Here's the link to my PCB Layout.

http://www.cjdawson76.btinternet.co....dicatorPCB.jpg

I haven't done any electronics since I were a lad (this is a great
reason to get back intot it!) - In those days I made PCBs using
transfers and etch resist pens. Is the photo-etching expensive to get
setup ? I bet the results are a lot better .. I'll do a little surfing
and see I think.


The most expensive bit that you really need is a UV light box. Buy one
for (roughly) £100 or make one for £50. The rest (etchant, developer,
boards, plastic trays...) is pretty cheap.

You can get good results for minimal outlay if you have a laser
printer using the "toner transfer" method - you print your circuit on
the laser (it has to be a laser) and iron it onto the board, the toner
sticks and acts as resist. Search for "pcb toner transfer" or
something like that, there are plenty of sites detailing the method.


Tim
--
Love is a travelator.
  #38  
Old April 28th 04, 11:12 AM
Andrew Cockburn
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Hmm. More expensive than I feared for the UV stuff - not worth it for
just a couple of boards.

The toner method sounds like fun though, and I have a laser printer, so
I'll give it a try - thanks :-)

Regards,

Andrew

Tim Auton wrote:
Andrew Cockburn wrote:

Ho Colin,


[snip]

Here's the link to my PCB Layout.

http://www.cjdawson76.btinternet.co....dicatorPCB.jpg


I haven't done any electronics since I were a lad (this is a great
reason to get back intot it!) - In those days I made PCBs using
transfers and etch resist pens. Is the photo-etching expensive to get
setup ? I bet the results are a lot better .. I'll do a little surfing
and see I think.



The most expensive bit that you really need is a UV light box. Buy one
for (roughly) £100 or make one for £50. The rest (etchant, developer,
boards, plastic trays...) is pretty cheap.

You can get good results for minimal outlay if you have a laser
printer using the "toner transfer" method - you print your circuit on
the laser (it has to be a laser) and iron it onto the board, the toner
sticks and acts as resist. Search for "pcb toner transfer" or
something like that, there are plenty of sites detailing the method.


Tim

  #39  
Old April 28th 04, 07:29 PM
Colin Dawson
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I dug it out and it takes 13.8v in - which probably means it works on
12v. Its worth a try before I fork out on a maplin or eBay one.


That'll work on the battery. 13.8v is the normal charging voltage
in a car. I don't think there will be a problem using it on your battery.

Regards

Colin Dawson
www.cjdawson.com


  #40  
Old April 28th 04, 07:32 PM
Colin Dawson
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Hi all


I haven't done any electronics since I were a lad (this is a great
reason to get back intot it!) - In those days I made PCBs using
transfers and etch resist pens. Is the photo-etching expensive to get
setup ? I bet the results are a lot better .. I'll do a little surfing
and see I think.


If you've got access to a lazer printer, there's a much cheaper solution
than photo etching.
If you take a look on the maplin website, take a look at the Press'N'Peel
transfer system.
You should get really good results from it. I used the photo-etching
method, because I like to do things that hardway.
also I only have an InkJet Printer.

At the very least it removes the urgency and lets me think about it in
more detail.
In all my vast experience of using the scope (1 night !) I haven't dewed
up yet, but
as soon as I do I know I'll wish I had the dew-heater handy so I'll
probably plug on
and get it going anyway. which means I also need to do the power thingy.


I've not really used the heater all that often, but it's been a godsend when
it's been needed.
The power thingy, isn't needed straight away either. You'll be able to tell
when the battery is wearing out
as the scope will start slow down and start to sound laboured long before
the battery gives out.

Good luck with that ! If I can't find the right kind of toolbox I may be
forced to do the same. I've got a mate who could help though, so maybe
for the price of a few beers I can get one together.


lol, sounds like my approach. I've got a mate who does alot of DIY, I'm
beggining to get a rought idea
of how the box will fit together, it's turning out to be a little more
complex, than I thought, but it should be
worth it in the end.

Regards

Colin Dawson
www.cjdawson.com


 




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