Help with Voltages, Amps etc.......

[Tim]

Over one hundred years ago (or so it seems) I had to drop out of Physics at 'A' level because I couldn't remember the formulas and I just dont have a head for figures (except the petite redheaded kind).

Now then, I purchased a 240v to 12v cigar socket adapter from Maplins a while ago, and promptly blew it up. The adapter has a max loading of 1000ma (1amp????????).

I bought it to run both my mount, and the dewshields, something which I now strongly suspect it wasn't designed to do :? .

SO, the question for those of you who know your electrical stuff, is what can I run on it?

The mount is an EQ6 Pro. I have no power figures for it, but I have heard on the grapevine that it can pull up to 3A with the motors going, I have no idea if that is true?

The dewshields are 2 x strips suitable for a C9.25. They are made by Astrozap (FLO's), and I run them from a dual channel controller. Ideally I would like to run these at MAX for the course of the night, as it seems the only way to prevent dewing when imaging the zenith. AT the moment I gradually jack the input up as the night goes on, but it just drains my power packs.

Is the Maplins adapter up to any of these jobs???? Or is there another way to do MAINS power to the mount + dewshields?

The battery packs seem capable of running the mount all night, but the dewshields really suck out the juice I think?

Now that winter is on its way I hope you guys can advise me! I lost the last part of a night last week due to the dew, and it's only gonna get worse....

Thanks

TJ

[Ant]

The 240v to 12v converters are not really up to the job. I have one rated at 5amp and it won't power the mount.

I have a HEQ5Pro which draws the same as the EQ6Pro - roughly two amp when slewing... I think that the maplin convertor (the ciggy socket version) is just Rubbish! #

What you need IMO is a Bench 12v DC Power supply... they are more expensive but they'll handle 10amp, maybe even 20amp depending on the one you buy.

Ant

[Beyond_Vision]

Are you able to run mains up to the scope. If you are I would recommend to use two 12V/5A mains power supplies from Maplins which have a cigarette lighter style output compatible with the lead for the EQ6. You will need at least 3 amps peak for the mount and around 2 amps for a CCD running on one pack and the other pack would run the heaters.

http://www.maplin.co.uk/Module.aspx?ModuleNo=42702&criteria=12v%20psu&doy=7m8

Regards

Kevin

[Beyond_Vision]

The 240v to 12v converters are not really up to the job. I have one rated at 5amp and it won't power the mount.

I have a HEQ5Pro which draws the same as the EQ6Pro - roughly two amp when slewing... I think that the maplin convertor (the ciggy socket version) is just Rubbish! #

What you need IMO is a Bench 12v DC Power supply... they are more expensive but they'll handle 10amp, maybe even 20amp depending on the one you buy.

Ant

5A should be plenty enough for the mount Ant the PSU may have been duff or possibly there is too much voltage drop across the cigarette lighter style connection. I have noticed on mine that the connection do get hot, which is indicative of a resitive connection ( this would lead to voltage drop when peak currents are drawn possibly causing mount handset to restart. I use mine for running my CCD cam and heaters and use a PSU I bought from SCS Astro's for the mount. It might be worth modifying the connection on these PSU to a DC Plug that will plug directly into the mount.

Regards

[centroid]

Ok TJ, back to Ohms Law we go then

Volts / Resistance = Amps

Volts / Amps = Resistance

Amps x Resistance = Volts

Amps x Volts = Watts or Volts (squared) / Resistance = Watts.

A 1 Amp supply is not 'man enough' to run an average dew heater band, and the manufacturer of the dew heater should state its required current, when supplied with 12 Volts.

240V ac to 12V DC converters come with various current output capabilities. I have 1 Amp, 5 Amp , 10 Amp and even 30 Amp ones 'knocking about'.

My 12" LX200R is powered by a 240V ac to 12V DC converter (aka Power Supply Unit), with a 1.2 Amp DC output, This simultaneously drives both RA and DEC motors, plus the electronics, without any problems.

My dew heater bands, one for the 12" and the other for the ED80, are powered from a 240 ac to 13.8V DC converter. The two heater bands, probably draw about 3 Amps, so the 5 Amp PSU is more than adequate.

12V is a nominal figure, and most "12V" power supplies are made to deliver a 13.8V regulated output. This is figure that appears accross the terminals of your 12V car battery, when the Alternator is running. So all of the "12V" equipment in your car such as the radio, is actually running on 13.8V when the engine is running. With the engine off, the Volatge falls back to that of the battery, which is 12V, made up from the six two volt cells, connected in series.

Hope the helps, as opposed to adding to your confusion.

BTW, you are correct in that 1 Amp = 1000 mA.

Dave

[cygnusx1]

Have you thought of a leisure battery instead?

Portable, less dangerous, no wires and danger of electrocution :shock: , and you can get a 110Ah for about £60-80 which will run all your equip for days!!

To me its a no brainer. I stay clear of mains.

[MikeP]

Did you see this thread TJ? http://stargazerslounge.com/index.php/topic,28952.0.html - I'm now using the PSU to run EQ6, dew strips and Atik. Works fine.

Mike

[RobH]

Hello TJ,

I completely melted a cigarrete lighter plug once trying to power up my dew bands.

After that, I thought I'd check how much power I was drawing....it turns out the one on the 14 inch will draw 8 amps at max output! Plus I have one on the finder and one on the guidescope.

I now use a 220-13.8 v 20 amp bench PSU for by dew bands, and run the scope and camera etc from a 110 AH liesure battery.

I tried running the dew bands off this at one time but they exhausted it over a long session.

I also put mains plugs on the dew heater gear as they're rated for a much higher amperage than the cigar lighter plugs.

Running your mount from a battery also gives a much more stable supply....mains voltage can vary quite a lot.

Cheers

Rob

[Ford Prefect]

Are you able to run mains up to the scope. If you are I would recommend to use two 12V/5A mains power supplies from Maplins which have a cigarette lighter style output compatible with the lead for the EQ6. You will need at least 3 amps peak for the mount and around 2 amps for a CCD running on one pack and the other pack would run the heaters.

http://www.maplin.co.uk/Module.aspx?ModuleNo=42702&criteria=12v%20psu&doy=7m8

Regards

Kevin

I have one of these and have had a few issues with it, for some reason it didn’t like powering the HEQ5 pro. It would work for 5 mins then the mount just shut off, it could just be an issue with mine !! L

TJ

If you are happy using mains power, i would recommend this from Bern at Modern Astronomy

100/240V AC Input 12V DC 5000mA Output psu - £29.99

http://www.modernastronomy.com/accessories.html#accPSU

Works a treat [/color]0pt][/color] Cheers Jon[/color]

[MikeP]

Rob's response made me think a bit about what I'm doing ....

I use a Kendrick controller (http://www.firstlightoptics.com/proddetail.php?prod=KendrickDF7) for my Astrozap dew strips . Not sure how to find out how much current it draws with the different dew strip configurations but its cigar lighter plug contains a 7A fuse (although the specifications indicate a max of 8A but requiring an upgraded fuse). The configurations are 11" on its own, 6" on its own or two 4" used together.

It would seem sensible to use a dedicated lighter socket attached to the PSU for the Kendrick and a separate one with splitter for the Atik and EQ6. At present, I just plug them in any old way.

Mike

[RobH]

Hello Mike, the reason my plug melted, rather than the fuse blowing, was that I'd already blown the fuse.....as the shops were shut, and I didn't have any spares......

you know what's coming next........

I wrapped silver foil round it and put it back in :oops:

.....shortly afterwards I had the old....'what's that burning smell' moment

What a plonker!!!!

Cheers

Rob

[Sam]

I'm sorry Rob but that really did make me laugh (only 'cause I've done the same thing with a portable electric fence fuse with very similar results).

[MikeP]

Rob,

What sort of silver foil do you recommend?

Mike

[Starflyer]

I find a length of 6" nail is a perfect fit

[Keagle]

I have one of http://www.maplin.co.uk/Module.aspx?ModuleNo=42702&criteria=12v%20psu&doy=7m8 those, and it works fine. This is my second one, the first one promptly started smoking when I tested it so I sent it back and got a replacement which seems to do the job for my EQ6 Pro.

[RobH]

Rob,

What sort of silver foil do you recommend?

Mike

I find it works best if it's had something tasty cooked in it !!!!

Rob

[Tim]

OK, it looks like I'm going to have to uprate things considerably. Thank you so much for all the advice!

Mains in the garden isn't too much of an issue, I rest the laptop on top of the hot-tub, which is rated at about 40A....

So I guess I'll grab a couple of PSU's. I'm not certain the dew bands have a rating on them, i'll check when it stops .

Rob, unbelievable!!! LOL! But I am certain that most of us would do the same given a clear night and no other option!

Cheers

TJ

[Tim]

OK, need a little more help here.....

If I go for one of the big PSU jobbies, like the Maplins 10A 13.8v XM19V

http://www.maplin.co.uk/Module.aspx?TabID=1&ModuleNo=231&doy=24m7

Then how do I get from the black and red connector thingies to the cigar socket plugs? Sorry to be thick, but my electrical connections usually involve lots of connector blocks and even more insualtion tape. I solder with all the skill of a blind armless alcoholic with St Vitus' Dance. I dont suppose for a minute there is a ready made lead????????

Thanks again

TJ

[MikeP]

TJ

I bought a couple of lighter socket things off the Internet somewhere - they had a cable (red wire and black wire) attached with two crocodile clips attached. I cut them off and replaced them with connectors that I bought from Halfords - round things with a hole in them. You just bare the wires and put them into the ends of the round things and squeeze them tight with pliers.

I hope this precise description completely meets your needs. If not, I'll see if I can post a piccy.

Mike

[MikeP]

Here's a picture (sorry about the quality). I've slid the blue plastic bit down on one of the wires so you can see the metal bit that the wire is crimped into.

Mike

(click to enlarge)

[Tim]

Hmm, ok, do those red and black connectors screw on/off then?

If I just used one supply, I'd need two cigar sockets, one for the dew controller, and one for the mount.

What cable is necessary to avoid voltage drop?

Are the cigar sockets up to the job or is it better to maybe hardwire a connection? What about in-line fuses? Necessary?

Thanks again. I'd like to get it right next time....

TJ

[MikeP]

TJ,

The connectors are just held on by being squeezed onto the wires with a pair of pliers. You could solder them if you wanted a more secure connection - I've not bothered.

I connect two sockets to the PSU. My Kendrick will be connected into one. I'll put a splitter into the other so that I can use it for the EQ6 and for the Atik.

The plugs that plug into the sockets have fuses inside them.

You could do away with the plugs and sockets but then you'd need some sort of inline fuse. Also, keeping the lighter plugs and sockets means its fairly easy to use battery packs if there is no mains power.

Can't answer your question about voltage drop.

Mike

[rigel1]

Is the 10A the right choice anyhow? I bought 2 of the 5A psu's, one for me mount, an' one for me dew htrs.

Although never really used the one for me htrs, one night I tried it to run a 12v hair dryer to remove dew from an e/p an me finder, Ah, blew the fuse immediately. Hence the 5A's are under powered for the h/d and have noticed that the inline fuse for the h/d is 15A anyhow, and is making me think about me own power supplies again. I think "think" before you buy TJ that at a later date you wish you had chosen something else.

I shall stick with what I have for the moment, an' try to find a lower Ampage h/d compared to the one I have, rather than move up to a 10A PSU.

The 10A should be ample to run your mount and dew htrs, but any more might start to overload it.

I am quite a novice in most astro matters but do like to play around with this an' that, but it's all usually down to preference and budget. And fun.

I hope my little bit of info helps in anyway.

Rigel1

[MikeP]

It seems that dew strips use the most current, so I thought I'd see how much mine use. The following information on Astrozap dew strips is taken from www.buytelescopes.com - Astrozap claim to use less power than other manufacturers, so if you use another brand these values may not apply.

Mike

[/td] [td]Length Wattage Amperage1.25" eyepieces 6.5" (16.5cm) 2.1W 0.25A2" eyepieces 9" (22.9cm) 4.2W 0.35A3" telescopes 13" (33.0cm) 6.0W 0.50A4" telescopes 15.5" (35.0cm) 7.3W 0.61A5" telescopes 16.75" (42.5cm) 7.9W 0.66A7" telescopes 25" (63.5cm) 11.8W 0.98A8" telescopes 30" (76.2cm) 14.0W 1.18A9.25" telescopes 33" (83.8cm) 15.5W 1.30A10" telescopes 36" (96.5cm) 17.8W 1.49A11" telescopes 40" (101.6cm) 18.8W 1.57A12" telescopes 43" (109.2cm) 20.2W 1.68A14" telescopes 49" (124.5cm) 23.0W 1.92A16" telescopes 55" (139.7cm) 25.8W 2.15A

[rigel1]

Hello TJ

Just done some browsing and thought you might be interested in JCM's set up in "Members Equipment Gallery / Set ups ready for use".

Have a look behind his scopes. Nice set up altogether.

Rigel1