[comabereni]

Quote:

Originally Posted by Nisbeth Another charger option here. I've tested and built the first circuit and it works fine. It might be a little rougher on the batteries than is necessary, but for such a simple circuit it's just fine. You can build it on piece of veroboard/stripboard quite easily. Set the charging current to something like 700 mA for a 7Ah battery and remember to put a small heatsink on the regulator.

This might be the most elegant solution discussed yet. I've already confessed here and elsewhere that I'm no DIY electronics guru (yet), but would this circuit be modifiable to charge two 12v batteries in series, i.e. @ 24 volts? If so, then this option moves to the top of the short list.

Thanks.

 

[PeterR]

Quote:

Originally Posted by Nisbeth IMO, building a charger should actually be an manageble task for most people - you included If you're nice to PeterR he might post the schematic for the one he build a while ago

I've been using it for over a year now to charge two 12V/3.5Ah SLAs connected in series, seems to work fine.

 

[comabereni]

Quote:

Originally Posted by PeterR I've been using it for over a year now to charge two 12V/3.5Ah SLAs connected in series, seems to work fine.

Excellent... thanks!

 

[Voodoochile]

I think you should build the Millett into a compartment under your parabolic mirror. Then you could run it off the same batteries, and the warmth from the buffers and tubes will also keep the dew off the mirror.

Anyone DIYer's who hves not clicked on comabereni's link in his sig ought to. Very cool work.

 

[comabereni]

Quote:

Originally Posted by Voodoochile I think you should build the Millett into a compartment under your parabolic mirror. Then you could run it off the same batteries, and the warmth from the buffers and tubes will also keep the dew off the mirror.

Right. And run all the wiring inside the tube and mount a headphone jack near the focuser. And don't forget the velcro tab next to that to hold the iPod on the telescope tube (right next to the computerized object database of course).

Darn it VC--now I'm actually thinking about how to make a musical telescope.

(Of course the amp under the primary mirror idea would certainly cause thermal issues--I can't even put a potentiometer inside the tube without causing tube current problems--ask me how I know

).
.
Quote:

Originally Posted by Voodoochile Anyone DIYer's who hves not clicked on comabereni's link in his sig ought to. Very cool work.

Thanks. I really love telescope making and astronomy.
.

 

[ITZBITZ]

Wow, those are some nice telescopes. With that size tube and mirror, I would imagine that I could see uranus from here.

 

[comabereni]

Quote:

Originally Posted by ITZBITZ Wow, those are some nice telescopes. With that size tube and mirror, I would imagine that I could see uranus from here.

Astronomy is an enjoyable pursuit that goes very well with portable headphone listening. (It also goes well with camping.

).

From this website, Observing the Solar System:

"Mars, Jupiter and Saturn are easily visible to the naked eye (except when they are close to the sun), and are great objects for small telescopes. Uranus is usually near the limit of naked eye detection, Neptune always requires optical aids, and Pluto is very unspectacular. In addition, binoculars will show four of Jupiter's 20 moons (the rest require large telescopes), and [even] a [very] small telescope will show two of Saturn's 18 moons [the 8" scopes on my site will show 5 of Saturn's moons]. Uranus' moons and all but one of Neptune's moons are effectively beyond the reach of small telescopes. Locating Uranus, Neptune, and Pluto requires careful searching using their co-ordinates and/or finder charts."

So, even though you can see them, through amateur equipment these planets (Neptune, Uranus, Pluto) look pretty much like small colored dots. Half the enjoyment of amateur astronomy is intellectual--it's thinking about what you are seeing, not necessarily seeing things looking like Hubble photos. Still, you can see a lot through a larger telescope--the Orion Nebula (M42) looks like a gorgeous grayscale sunset through a 16" telescope (diameter of mirror), and through a decent 4" to 8" telescope you can easily see lots of detail in the Great Red Spot on Jupiter, separations in the rings of Saturn, just as examples. Of course you can also see detail in galaxies (spiral arm structure), hundreds of the thousands of stars in globular clusters, nebulae, double stars (lots of those), and the moon at high magnification is breathtaking enough that you never get tired of looking at it.

Thanks!

 

[slindeman]

Quote:

The necessary heater current for each tube is 150mA, for a total of 300mA

Since the heaters are in series, I'm pretty sure the total remains 150mA. Each drops half the voltage. Add 30-40mA if you are running the buffers in high bandwidth mode, and you come close to 200mA total. I don't see why it wouldn't work with normal nimh batteries as long as you don't mind charging them every 8-10 hours.

 

[Voodoochile]

Yes, the buffers are in wideband mode. You could cut it back a bit if desired, though. Pete talks about jumpered or open, but no reason you could not throw a 220 ohm or so resistor in there. I think it's pretty academic relative to the draw of the rest of the amp.

 

[comabereni]

Thanks everyone for your help with this. When the Millett amp gets here, because I'm in the middle of remodeling my home, I'm going to just plug it into a wall wart for a few weeks. That will give me plenty of opportunity to listen to it that way. Then I'll pick up this chassis/battery-operation project when I have a bit more time and see what I can do with it.

I found an old thread that mentioned some of the difficulties with using LEDs on the same power supply with this amp, so my mind is turning on how to do that too. I don't want to under-voltage this at all, so since 24v DC is at the bottom end of adequate, it might be less desirable than perhaps three 9v in series, or even seven 4v in series (and maybe a separate 8th 4v just to run the LEDs). I'd likely have to build the charge circuit for certain if I went either of those routes (no problem). I might also have some extra headroom for LEDs without having to run them from a separate battery if I went that way.

I'm at the point now where I should probably pick up a book on understanding electronics schematics and buy a multimeter--to give you an idea of where I am coming from. I think this amp is going to be a great place for me to jump into DIY head/hi-fi. I see what I'll be doing with my electronics engineer brother-in-law this Thanksgiving

.

Thanks again.

 

[flecom]

btw my millet with 2x 12AE6A's and the bias at 16.2V uses 180mA +/- like 5mA depending on how loud it is etc @ 24VDC (just measured it with my multimeter)

this is driving a pair of 250ohm/ch phones

 

[comabereni]

Quote:

Originally Posted by flecom btw my millet with 2x 12AE6A's and the bias at 16.2V uses 180mA +/- like 5mA depending on how loud it is etc @ 24VDC (just measured it with my multimeter) this is driving a pair of 250ohm/ch phones

Good to know. Thanks. I'm thinking about making another one of these now and putting them both on battery power.