Power issue

[Simon Dunsmore]

Hi Folks,

I could do with a little help from any electrical boffins out there.

I usually run my mount and gear from the mains when imaging at home. However, I plan to take the rig out to a dark sky sight, so decided to build a portable power supply.

I had a 45amp hour car battery going spare so purchased some cigar lighter sockets and 2x 12v switches and following a wiring diagram installed the components in a suitable plastic container.

So far so good, when I switch it on, the switches and LEDs in the sockets light up. Output from the battery is measuring 12.75v but no power to the mount. I'm using the same leads that I use with the mains set up so I know they're good.

Any suggestions???

Thanks 

Simon 

 

Edited December 14, 2021 by Simon Dunsmore
Error

[bosun21]

6 minutes ago, Simon Dunsmore said:

Hi Folks,

I could do with a little help from any electrical boffins out there.

I usually run my mount and gear from the mains when imaging at home. However, I plan to take the rig out to a dark sky sight, so decided to build a portable power supply.

I had a 45amp hour car battery going spare so purchased some cigar lighter sockets and 2 13v switches and following a wiring diagram installed the components in a suitable plastic container.

So far so good, when I switch it on, the switches and LEDs in the sockets light up. Output from the battery is measuring 12.75v but no power to the mount. I'm using the same leads that I use with the mains set up so I know they're good.

Any suggestions???

Thanks 

Simon 

 

Can you post the wiring diagram as there is undoubtedly something wrong with the connections inside your box 

[Simon Dunsmore]

1 hour ago, bosun21 said:

Can you post the wiring diagram as there is undoubtedly something wrong with the connections inside your box 

Hi and thanks for your quick reply. Wiring diagram attached. I'm not sure if this would make any difference but I repeated this for two sockets. 

Please forgive my ignorance, but would the switches and sockets still light up if wired incorrectly?

 

Thanks

Simon 

Wiring Diagram.pdf

Edited December 14, 2021 by Simon Dunsmore
error

[bosun21]

If you have followed this and your connections are tight and secure then it’s either the battery posts need cleaned and check the connection to them is good. Failing that then it’s the cigar connections not making contact. Out of curiosity what condition is the battery (age etc)

[Simon Dunsmore]

3 minutes ago, bosun21 said:

If you have followed this and your connections are tight and secure then it’s either the battery posts need cleaned and check the connection to them is good. Failing that then it’s the cigar connections not making contact. Out of curiosity what condition is the battery (age etc)

The battery is pretty old but the output seems good 12.75v I'll check the sockets but they do light up when the switch is flicked.

Thanks again

Simon 

[bosun21]

1 minute ago, Simon Dunsmore said:

The battery is pretty old but the output seems good 12.75v I'll check the sockets but they do light up when the switch is flicked.

Thanks again

Simon 

The light (led) only shows that the power is reaching the connection not leaving it 

[Budgie1]

Have you got a multi-meter to check there's power coming out of the sockets? It will also tell you that you have the polarity correct, The switch & LED will both light up when power is put through them in either direction but your mount etc needs the correct polarity.

[Simon Dunsmore]

4 minutes ago, Budgie1 said:

Have you got a multi-meter to check there's power coming out of the sockets? It will also tell you that you have the polarity correct, The switch & LED will both light up when power is put through them in either direction but your mount etc needs the correct polarity.

Thanks for the reply. Do I just touch one of the tester prongs on the tab on the rear (inside) and another on the wall (inside) of the socket to test?

[M40]

Is there any chance you could have used the wrong connections on the switch itself? 

[Budgie1]

10 minutes ago, Simon Dunsmore said:

Thanks for the reply. Do I just touch one of the tester prongs on the tab on the rear (inside) and another on the wall (inside) of the socket to test?

Yep, the red (+) prong should got in the centre contact inside the socket and the black (-) on the metallic part of the sidewall. 

If the needle or readout (LCD version) goes to a negative reading then the polarity is the wrong way round.

2 minutes ago, M40 said:

Is there any chance you could have used the wrong connections on the switch itself? 

Good point, how many connections are there on the back of the switch, 2 or 3?

[M40]

7 minutes ago, Simon Dunsmore said:

Thanks for the reply. Do I just touch one of the tester prongs on the tab on the rear (inside) and another on the wall (inside) of the socket to test?

Remove anything you have plugged into the socket. Set your meter to DC, put one of the meter leads on the -ve of the battery and the other on the +ve. If you get a reading the battery is ok. Leave the lead on the -ve and go to the fuse and check both sides of the fuse then go to the socket. If all is good, put one of your leads on the +ve of the battery and go to the switch, check both sides of the switch with it on and off then go to the socket. HTH

[Simon Dunsmore]

24 minutes ago, Budgie1 said:

Yep, the red (+) prong should got in the centre contact inside the socket and the black (-) on the metallic part of the sidewall. 

If the needle or readout (LCD version) goes to a negative reading then the polarity is the wrong way round.

Good point, how many connections are there on the back of the switch, 2 or 3?

There are three terminals on the switch. Presently the middle one is left blank

[AstroKeith]

10 minutes ago, Simon Dunsmore said:

There are three terminals on the switch. Presently the middle one is left blank

There's your problem.....

The centre is the common, use that one and either end.

[Simon Dunsmore]

2 minutes ago, AstroKeith said:

There's your problem.....

The centre is the common, use that one and either end.

Thanks for your reply. Sorry, I'm not sure I understand. Any chance you scribble a  quick diagram?

[Budgie1]

12 minutes ago, Simon Dunsmore said:

There are three terminals on the switch. Presently the middle one is left blank

Okay, so this could be the issue.

Normally with the three terminal switches they are for:

• Ground (Earth connection to the battery)
• Power (12v supply from the battery)
• Accessory (12v supply to the cigar socket).

It's figuring out which is which. They're normally marked GND, ACC & PWR on the switch somewhere.

[Capt Slog]

41 minutes ago, Simon Dunsmore said:

Thanks for your reply. Sorry, I'm not sure I understand. Any chance you scribble a  quick diagram?

There are quite a few configurations of switches.  But it sounds as if the one you have connects the middle terminal to one side or the other when the switch is 'thrown' (and at the same time disconnects the opposite side).  The middle terminal then is known as the 'common'.  If you have the wires connected at either end of the switch, they'll never make a circuit.  EDIT  But this is just a guess, a photo would help.  As might this drawing 

In your case, the battery would be connected to 'common' and you use either 'A' or 'B' for the "output", it doesn't matter which, one of the terminal will remain unused.

You will also have to be aware that the switch will not like currents over a certain rating.  If you operate the switch under load, the contacts will burn and it will eventually ( or sooner ) stop working.

Edited December 14, 2021 by Capt Slog

[wulfrun]

Odd way to wire it up! Conventional method would be negative direct to socket and positive to fuse, then on to switch, then on to socket. If the switch is a simple "spdt" type, the centre terminal connects to the incoming power (from fuse) and the switched side goes from either end terminal to the outlet socket - the choice depends which switch position you want "on" to be.

Be careful checking voltages with a test meter, they draw almost zero power so will still show a voltage even when there's a duff connection somewhere. Use a test lamp or connect an actual load once you are certain the polarity is correct, to be sure there's actual power.

EDIT: Agreed a photo of your switches would be helpful

Edited December 14, 2021 by wulfrun
typo, clarity

[Capt Slog]

43 minutes ago, Budgie1 said:

Okay, so this could be the issue.

Normally with the three terminal switches they are for:

• Ground (Earth connection to the battery)
• Power (12v supply from the battery)
• Accessory (12v supply to the cigar socket).

It's figuring out which is which. They're normally marked GND, ACC & PWR on the switch somewhere.

I don't understand what you mean here.  But I'd have thought that if you wired a switch in this way, at some switch position you could connect battery positive to battery negative which would be exciting.

[Budgie1]

11 minutes ago, Capt Slog said:

I don't understand what you mean here.  But I'd have thought that if you wired a switch in this way, at some switch position you could connect battery positive to battery negative which would be exciting.

No, the only difference between the three terminal switch & a two terminal switch is the Ground terminal.

The three terminal can be grounded on the negative terminal of a battery or an earthing point on a car body. The actual power supply switching is done between the PWR & ACC terminals.

THIS SITE may explain it better than I can.

[teoria_del_big_bang]

Easiest wat to check if it is just the switch wired incorrectly is to take is out for now and just connect the two wires together and see if you can power your mount.
If that works then yes you need to see how the switch needs wiring.
Have you soldered the switch terminals or used spade connectors ?
If soldered then just remove them for now and connect the two wires together, if spade connectors just remove them on somehow connect the two together.

ALLTHOUGH, the fact the LEDs in the socket come on when the switch is on and go off when the switch is off does suggest the switch is correctly wired.

If you are happy the switch is wired ok then  you really need a volt meter and check the voltage where you can (even at battery terminals)  with it connected to the mount and mount switched on.
You may find that the output is 12.75V when just powering the LED's with a few milliamps but when it has to deliver a reasonable current of an amp or so the voltage may drop drastically.

You say the battery is quite old - has it been regularly charged ?
If the battery has been stored for months without regular charging than the battery could be useless. Car batteries, or leisure batteries need regularly topping up when stored to keep them in good condition and also should never be fully run down when in use.

Also 12.75V is quite low for a car battery when not supplying current, a fully charged battery is around 13.8 V when not supplying any current.

Steve 

 

Edited December 14, 2021 by teoria_del_big_bang

[Capt Slog]

10 minutes ago, Budgie1 said:

No, the only difference between the three terminal switch & a two terminal switch is the Ground terminal.

The three terminal can be grounded on the negative terminal of a battery or an earthing point on a car body. The actual power supply switching is done between the PWR & ACC terminals.

THIS SITE may explain it better than I can.

I see, you're talking about 'lighted switches'. 

( clarification for the OP, this is a switch with an LED built in, lights when switched on or could be permanently lit to show location, or other combinations).

 

We don't know if that's what he's using, we need more info 

[ONIKKINEN]

Cant help with the switch problems, but thought id say that without regulation of some sort you will probably run into power problems faster than you would imagine. Just an unregulated "dumb" battery might read 12.75V now, but will drop below 12V really quickly once you start to draw power from it. Its entirely possible that your mount starts having problems slewing in under an hour. Especially true if its cold outside, you can get under 12V from a battery that still has most of its charge left and there is really nothing you can do about it other than have some sort of voltage regulation going on.

[Simon Dunsmore]

7 minutes ago, Capt Slog said:

I see, you're talking about 'lighted switches'. 

( clarification for the OP, this is a switch with an LED built in, lights when switched on or could be permanently lit to show location, or other combinations).

 

We don't know if that's what he's using, we need more info 

Hi, Yes it's a with with a built in LED that lights up when toggled to the ON position

[teoria_del_big_bang]

As the switch seems to be the main topic of replies if you recently bought the switch do you have a link to what switch you used, or at least a picture of the front and rear of the switch.

If there is an LED in the switch normally you have to supply it with a ground and 12V in order to light up the LED in the switch but your diagram only shows a ground wire to it. But it could still light up because it get some positive voltage through the mount or maybe even the led in the socket but this still may not give the mount a proper ground as everything is via the led.

You may not understand what I mean so a link or pics will quickly get this cleared up.

Steve

[teoria_del_big_bang]

4 minutes ago, Simon Dunsmore said:

Hi, Yes it's a with with a built in LED that lights up when toggled to the ON position

Then I would think you need three wires to it, please let us know exactly which switch you are using.

Steve