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LX90 First Light (longish)



 
 
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  #21  
Old April 26th 04, 10:09 PM
Chris Taylor
external usenet poster
 
Posts: n/a
Default

"""I've taken a quick look at an alarm battery that B&Q do. It was 12v
rated at 1.2Ah, which is seriously under powered for the scope, I've tested
and it pulls 2amps when slewing in both alt and azi."""

1.2 Ah (Amp.hour) will offer a continuous 1.2 Amps for 1 hour, or a
continuous 2.4 Amps for 30 Minutes, or a continuous 0.12Amps for 10 Hours.
I've not run the 1.2Ah flat yet and have had it running continuously for
over 6 Hrs in one sitting. What was the current draw while tracking?

Regards


Chris


"Colin Dawson" wrote in message
...

Hi Andrew

My immediate need is to not have to buy another set of those damn C
cells, so I think I'll pick up a small lead-acid battery and hook it up
as per your power cable specs, then think some more about my master
project. Do you know anywhere on the web that stocks a good range of
suitable batteries ? Chris mentioned he used an alarm battery from B&Q,
that will probably do for starters, but I can imagine I'll need
something fairly hefty when I get all of the above in and running !


I've taken a quick look at an alarm battery that B&Q do. It was 12v rated
at 1.2Ah, which is seriously under powered for the scope, I've tested and

it
pulls 2amps when slewing in both alt and azi.

One of those car jump starters will do the job in the first instance.

That's
what my 17Ah is in. It'll provide all the power that you need, until you
start playing with bum warmers, also when you manage to finish your master
project, it can be retired to the car, just incase of a flat battery :-).
The product code is L52AT and it only costs 19.99 including charger!

A word of warning about the power cable - Make sure that the polarity if
correct. I can't re-iterate this enough, get it wrong and the electrics

of
the scope could get damaged! I've seen it happen!!!!! (not to my scope
though)



Let me guess. The blinking lights. They're always popular.

Yep ;-) They look pretty simple to rustle up and would instantly label
me as a techno-geek. Is geekery possible in the telescope world ?


Erm... geekery is a compulsary qualification needed before you're even
allowed your FIRST scope! :-P

You might be interested that Maplin also do a laptop power converter that
runs from 12v. I've got one when they were on offer, and it's great. I
think it was N11BB from the maplin site, but it was on offer at £20.

Regards

Colin Dawson
www.cjdawson.com




  #22  
Old April 26th 04, 11:12 PM
Colin Dawson
external usenet poster
 
Posts: n/a
Default


"Jonathan Silverlight" wrote
in message ...
In message , Colin Dawson
writes

A word of warning about the power cable - Make sure that the polarity if
correct. I can't re-iterate this enough, get it wrong and the electrics

of
the scope could get damaged! I've seen it happen!!!!! (not to my scope
though)


I've seen it happen too, but is there some good reason why the
manufacturer (or a DIY-er) can't incorporate a diode in the circuit so
reversing the polarity does no harm?
--
Save the Hubble Space Telescope!
Remove spam and invalid from address to reply.


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. 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. Basically No reason at all.

As for the DIY'ers. We all know about it already, and shout at people who
get new scopes, just to make sure the message is put across. Once we've
built the cables - with plugs on both ends, the diode no longer serves a
purpose. But it would still be nice to have one just in case.

Regards

Colin Dawson
http://www.cjdawson.com/


  #23  
Old April 26th 04, 11:17 PM
Colin Dawson
external usenet poster
 
Posts: n/a
Default


"Andrew Cockburn" wrote in message
-service-com...

You might be interested that Maplin also do a laptop power converter

that
runs from 12v. I've got one when they were on offer, and it's great.

I
think it was N11BB from the maplin site, but it was on offer at £20.


Just remembered that I already have an in-flight laptop inverter that
would do the job - do you (or anyone lese) happen to know what voltage
they use for power on planes ? If its 12v I'm all set ...

Regards,

Andrew



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.

Regards

Colin Dawson
www.cjdawson.com


  #24  
Old April 26th 04, 11:31 PM
Colin Dawson
external usenet poster
 
Posts: n/a
Default

(Duel of fates playing in background) IT'S WORKING, IT'S WORKING!

Woohoo.

OK, guy's here's a couple of circuit diagrams that I'll share. The first
should be coupled with the K8004 circuit used in my dew heater, this will
provide a nice bargraph showing the setting of the 1K Pot. (hmmm pretty red
lights). The second is the 12V battery voltage monitor that I just
finished. I've made both circuits up onto PCB's so I know that they work
perfectly.

K8004 Setting Bar
http://www.cjdawson76.btinternet.co....tdrivenbar.jpg

Battery Monitor
http://www.cjdawson76.btinternet.co....rIndicator.jpg


I've got the tools that I need to make these up into proper PCB's, they've
have turned out really well. I've spread the LED's over about 10cm, it
should show up easily in the dark. Oh yeah, I got these circuit from the
web then modified them slightly to fix some issues that I noticed with them.

Next stage of my master project is to build the box to put the box that will
house all the parts. This is going to take quite a while to design, but it
should turn out well. At least the electonics are all completed.


Regards

Colin Dawson
www.cjdawson.com


"Andrew Cockburn" wrote in message
-service-com...
Can't wait to see how you did it, sounds cool - good luck getting it
working !

Andrew

Colin Dawson wrote:

I saw in one of your messages that you are thinking about a charge
indicator. That's one of the things that I'm putting into my box.

Also
I'm adding a circuit to show the current setting of the dew heater.

Each
circuit will pull about 20mA of power from the battery, so it's not even
worth thinking about :-) Even in high power mode, when it shows a

pretty
bar graph, it still pulls about 100mA with all ten LED's lit. I'll be
posting up the circuit diagrams once I've got it all working.

(hopefully tonight!)

Regards

Colin.




  #25  
Old April 26th 04, 11:41 PM
Colin Dawson
external usenet poster
 
Posts: n/a
Default

It was a while since to took the readings, it pulled hardly any juice when
tracking, less that 0.25 of an amp I think. I've got a couple of questions
for you... when your using your scope I take it that you tend to spend a
serious amount of time traking a single object right?

During the evening you'll start with the battery at full charge, slewing
like this the scope will be really perky, as the night draws on, the battery
cools, the scope draws it's power. If you try slewing at the end of the
evening after your six hours does the scope sound just as perky as at the
beginning of the night? I tend to target several objects in a session,
even using my 7.2Ah battery the scope sounds laboured (the tone of the
motors is lower) at the end of the evening.

It's an observation that I made when I first got the scope, it's especially
bad with the 'C' Cells, I've still got a couple of packs unopened, as I
refuse to use them in my scope... besides they might leak and damage my
baby. :-)

Regards

Colin Dawson
www.cjdawson.com


"Chris Taylor" wrote in message
news:iUejc.213$fw5.176@newsfe1-win...
"""I've taken a quick look at an alarm battery that B&Q do. It was 12v
rated at 1.2Ah, which is seriously under powered for the scope, I've

tested
and it pulls 2amps when slewing in both alt and azi."""

1.2 Ah (Amp.hour) will offer a continuous 1.2 Amps for 1 hour, or a
continuous 2.4 Amps for 30 Minutes, or a continuous 0.12Amps for 10 Hours.
I've not run the 1.2Ah flat yet and have had it running continuously for
over 6 Hrs in one sitting. What was the current draw while tracking?

Regards


Chris


"Colin Dawson" wrote in message
...

Hi Andrew

My immediate need is to not have to buy another set of those damn C
cells, so I think I'll pick up a small lead-acid battery and hook it

up
as per your power cable specs, then think some more about my master
project. Do you know anywhere on the web that stocks a good range of
suitable batteries ? Chris mentioned he used an alarm battery from

B&Q,
that will probably do for starters, but I can imagine I'll need
something fairly hefty when I get all of the above in and running !


I've taken a quick look at an alarm battery that B&Q do. It was 12v

rated
at 1.2Ah, which is seriously under powered for the scope, I've tested

and
it
pulls 2amps when slewing in both alt and azi.

One of those car jump starters will do the job in the first instance.

That's
what my 17Ah is in. It'll provide all the power that you need, until you
start playing with bum warmers, also when you manage to finish your

master
project, it can be retired to the car, just incase of a flat battery

:-).
The product code is L52AT and it only costs 19.99 including charger!

A word of warning about the power cable - Make sure that the polarity if
correct. I can't re-iterate this enough, get it wrong and the electrics

of
the scope could get damaged! I've seen it happen!!!!! (not to my scope
though)



Let me guess. The blinking lights. They're always popular.

Yep ;-) They look pretty simple to rustle up and would instantly label
me as a techno-geek. Is geekery possible in the telescope world ?


Erm... geekery is a compulsary qualification needed before you're even
allowed your FIRST scope! :-P

You might be interested that Maplin also do a laptop power converter

that
runs from 12v. I've got one when they were on offer, and it's great. I
think it was N11BB from the maplin site, but it was on offer at £20.

Regards

Colin Dawson
www.cjdawson.com






  #26  
Old April 27th 04, 07:57 AM
Chris Taylor
external usenet poster
 
Posts: n/a
Default

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.

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.

Regards


Chris

"Colin Dawson" wrote in message
...
It was a while since to took the readings, it pulled hardly any juice when
tracking, less that 0.25 of an amp I think. I've got a couple of

questions
for you... when your using your scope I take it that you tend to spend

a
serious amount of time traking a single object right?

During the evening you'll start with the battery at full charge, slewing
like this the scope will be really perky, as the night draws on, the

battery
cools, the scope draws it's power. If you try slewing at the end of the
evening after your six hours does the scope sound just as perky as at the
beginning of the night? I tend to target several objects in a

session,
even using my 7.2Ah battery the scope sounds laboured (the tone of the
motors is lower) at the end of the evening.

It's an observation that I made when I first got the scope, it's

especially
bad with the 'C' Cells, I've still got a couple of packs unopened, as I
refuse to use them in my scope... besides they might leak and damage my
baby. :-)

Regards

Colin Dawson
www.cjdawson.com


"Chris Taylor" wrote in message
news:iUejc.213$fw5.176@newsfe1-win...
"""I've taken a quick look at an alarm battery that B&Q do. It was 12v
rated at 1.2Ah, which is seriously under powered for the scope, I've

tested
and it pulls 2amps when slewing in both alt and azi."""

1.2 Ah (Amp.hour) will offer a continuous 1.2 Amps for 1 hour, or a
continuous 2.4 Amps for 30 Minutes, or a continuous 0.12Amps for 10

Hours.
I've not run the 1.2Ah flat yet and have had it running continuously for
over 6 Hrs in one sitting. What was the current draw while tracking?

Regards


Chris


"Colin Dawson" wrote in message
...

Hi Andrew

My immediate need is to not have to buy another set of those damn C
cells, so I think I'll pick up a small lead-acid battery and hook it

up
as per your power cable specs, then think some more about my master
project. Do you know anywhere on the web that stocks a good range of
suitable batteries ? Chris mentioned he used an alarm battery from

B&Q,
that will probably do for starters, but I can imagine I'll need
something fairly hefty when I get all of the above in and running !

I've taken a quick look at an alarm battery that B&Q do. It was 12v

rated
at 1.2Ah, which is seriously under powered for the scope, I've tested

and
it
pulls 2amps when slewing in both alt and azi.

One of those car jump starters will do the job in the first instance.

That's
what my 17Ah is in. It'll provide all the power that you need, until

you
start playing with bum warmers, also when you manage to finish your

master
project, it can be retired to the car, just incase of a flat battery

:-).
The product code is L52AT and it only costs 19.99 including charger!

A word of warning about the power cable - Make sure that the polarity

if
correct. I can't re-iterate this enough, get it wrong and the

electrics
of
the scope could get damaged! I've seen it happen!!!!! (not to my

scope
though)



Let me guess. The blinking lights. They're always popular.

Yep ;-) They look pretty simple to rustle up and would instantly

label
me as a techno-geek. Is geekery possible in the telescope world ?

Erm... geekery is a compulsary qualification needed before you're even
allowed your FIRST scope! :-P

You might be interested that Maplin also do a laptop power converter

that
runs from 12v. I've got one when they were on offer, and it's great.

I
think it was N11BB from the maplin site, but it was on offer at £20.

Regards

Colin Dawson
www.cjdawson.com








  #27  
Old April 27th 04, 08:00 AM
Chris Taylor
external usenet poster
 
Posts: n/a
Default


"""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...

Regards


Chris

"Colin Dawson" wrote in message
...

"Jonathan Silverlight"

wrote
in message ...
In message , Colin Dawson
writes

A word of warning about the power cable - Make sure that the polarity

if
correct. I can't re-iterate this enough, get it wrong and the

electrics
of
the scope could get damaged! I've seen it happen!!!!! (not to my

scope
though)


I've seen it happen too, but is there some good reason why the
manufacturer (or a DIY-er) can't incorporate a diode in the circuit so
reversing the polarity does no harm?
--
Save the Hubble Space Telescope!
Remove spam and invalid from address to reply.


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. 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. Basically No reason at all.

As for the DIY'ers. We all know about it already, and shout at people who
get new scopes, just to make sure the message is put across. Once we've
built the cables - with plugs on both ends, the diode no longer serves a
purpose. But it would still be nice to have one just in case.

Regards

Colin Dawson
http://www.cjdawson.com/




  #28  
Old April 27th 04, 08:34 AM
Andrew Cockburn
external usenet poster
 
Posts: n/a
Default

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 ?

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

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 ...

Regards,

Andrew

Colin Dawson wrote:
(Duel of fates playing in background) IT'S WORKING, IT'S WORKING!

Woohoo.

OK, guy's here's a couple of circuit diagrams that I'll share. The first
should be coupled with the K8004 circuit used in my dew heater, this will
provide a nice bargraph showing the setting of the 1K Pot. (hmmm pretty red
lights). The second is the 12V battery voltage monitor that I just
finished. I've made both circuits up onto PCB's so I know that they work
perfectly.

K8004 Setting Bar
http://www.cjdawson76.btinternet.co....tdrivenbar.jpg

Battery Monitor
http://www.cjdawson76.btinternet.co....rIndicator.jpg


I've got the tools that I need to make these up into proper PCB's, they've
have turned out really well. I've spread the LED's over about 10cm, it
should show up easily in the dark. Oh yeah, I got these circuit from the
web then modified them slightly to fix some issues that I noticed with them.

Next stage of my master project is to build the box to put the box that will
house all the parts. This is going to take quite a while to design, but it
should turn out well. At least the electonics are all completed.


Regards

Colin Dawson
www.cjdawson.com


"Andrew Cockburn" wrote in message
-service-com...

Can't wait to see how you did it, sounds cool - good luck getting it
working !

Andrew

Colin Dawson wrote:


I saw in one of your messages that you are thinking about a charge
indicator. That's one of the things that I'm putting into my box.


Also

I'm adding a circuit to show the current setting of the dew heater.


Each

circuit will pull about 20mA of power from the battery, so it's not even
worth thinking about :-) Even in high power mode, when it shows a


pretty

bar graph, it still pulls about 100mA with all ten LED's lit. I'll be
posting up the circuit diagrams once I've got it all working.

(hopefully tonight!)

Regards

Colin.





  #29  
Old April 27th 04, 10:47 AM
Martin Brown
external usenet poster
 
Posts: n/a
Default

In message , Colin Dawson
writes

"Jonathan Silverlight" wrote
in message ...
In message , Colin Dawson
writes

A word of warning about the power cable - Make sure that the polarity if
correct. I can't re-iterate this enough,


I've seen it happen too, but is there some good reason why the
manufacturer (or a DIY-er) can't incorporate a diode in the circuit so
reversing the polarity does no harm?


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. 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. Basically No reason at all.


Common or garden silicon diodes drop 0.6v forward biassed which is a bit
marginal on a 12v supply. You really need a low voltage drop Schottky
diode (eg 1N5822 3A rated) in series which will drop somewhere around
0.3v..

That or connect the protection diode in parallel across the input
terminals so that it shorts out the PSU if applied incorrectly and
immediately blows the fuse. This would need testing to establish that it
worked well enough!! Some touchy components may croak with modest
reverse polarity voltages applied even for an instant.

As for the DIY'ers. We all know about it already, and shout at people who
get new scopes, just to make sure the message is put across. Once we've
built the cables - with plugs on both ends, the diode no longer serves a
purpose. But it would still be nice to have one just in case.


According to their current adverts Bull electrical have some various
sized surplus lead acid batteries on offer up to 17Ah.
http://www.bullnet.co.uk
Their prices are usually good, but check prices against Maplin.

Regards,
--
Martin Brown
  #30  
Old April 27th 04, 02:23 PM
Graham W
external usenet poster
 
Posts: n/a
Default


"Colin Dawson" wrote in message
...

"Jonathan Silverlight"

wrote
in message ...
In message , Colin Dawson
writes

A word of warning about the power cable - Make sure that the polarity

if
correct. I can't re-iterate this enough, get it wrong and the

electrics
of
the scope could get damaged! I've seen it happen!!!!! (not to my

scope
though)


I've seen it happen too, but is there some good reason why the
manufacturer (or a DIY-er) can't incorporate a diode in the circuit so
reversing the polarity does no harm?
--
Save the Hubble Space Telescope!
Remove spam and invalid from address to reply.


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.

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.

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.

Further luxuries may include an LED in series with another small diode
and 1K resistor and wired across the input wires to indicate that the
supply is the right polarity and delivering a bit of current.

A small switch in series with the relay coil could effectively control the
switching On/Off of the whole rig without having to handle the whole
load current, too.

HTH

--
Graham W http://www.gcw.org.uk/ PGM-FI page updated, Graphics Tutorial
WIMBORNE http://www.wessex-astro-society.freeserve.co.uk/ Wessex
Dorset UK Astro Society's Web pages, Info, Meeting Dates, Sites & Maps
Change 'news' to 'sewn' in my Reply address to avoid my spam filter.

 




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