12V 5A dc extension cable to power ASIair

[Ouroboros]

Anyone recommend a supplier of 12V dc extension cable 2.1*5.5mm (female socket one end, male plug the other) rated at 5A?  I need at least 5 metres, preferably longer. I’ve tried standard 5m and 10m cables and they reduce the voltage down to below 12V, which isn’t enough for the ASIair to function stably, or even at all with one cable. The ASIair is fine powered directly without the extension cable.  I want to avoid running mains power out to the mount, or using a power pack. 

If I can’t buy one I’ll have to make a cable up with suitable double core cable and connectors. Just thought I’d try SGL first. 😀

[SthBohemia]

Fabricate the cord from heavy duty speaker cable or run the mains to the PSU placed close to the mount. I fabricated  a cord using speaker wire running a similar distance to yourself, but used inferior quality wire. Just compensated by adjusting the switched power supply (12v@8A) for a Skywatcher EQ6 up to 13.5 volts. Must make a better cable... Someday...

[DaveL59]

losses in the cable over that length will always be an issue with this type of plug as they aren't really designed to take heavy gauge wire and the plug/socket connection isn't all that great either so more losses per connection in the run. Can you not as suggested either move the PSY closer, or perhaps use a direct run of heavier gauge wire from the PSU out to the far end terminated in something like power-pole and make a power-pole to 2.1/5.5 for the 'last mile' into the ASlair?

[iapa]

I’m with the other responders; use a mains extension with integral circuit breaker.

[Budgie1]

If you're worried about dew with a mains extension then a waterproof extension or normal extension lead into a Dri-Box should do the trick.  

[iapa]

I use these

https://smile.amazon.co.uk/gp/product/B004R255VQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

[fifeskies]

rewirable adapters allow you to easily make up any length of high current DC cable without having to solder large cables onto small fiddly tabs.

I use 1mm 2-core rubber cable (or 2-core 0.75mm for shorter runs)

It can be a good idea to also use an inline fuse.

 

 

 

 

Edited July 6, 2022 by fifeskies

[SthBohemia]

1 hour ago, iapa said:

I use these

https://smile.amazon.co.uk/gp/product/B004R255VQ/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1

 

😞 42 quid for a bit of wire! I am obviously totally out of touch with UK prices...

[Carbon Brush]

A couple of comments to get the problem into perspective.

A 1mmsq cross section copper wire has about 180milliohms resistance at 20C.
You can easily recalculate for thinner/thicker wires.
Ohms law gives you 0.18V drop at 1A, or 0.9V at 5A.

On a -10C night, the number above becomes 160mohms.
For solar observers, at 40C it is more like 190mohms.

The above calulation relates only to the wire. Not accounting for resistance in assorted connections.

A further consideration is that the load (whether mount computer or dew heater) does not take constant current.

An easily understood example being a dew heater turning on/off as the power is adjusted.
The heater might take 5A. But when running 20% power, it may cycle 1sec ON and 4sec OFF.
When considering power supply capability and cable voltage drop, it is the ON figure that you must use.

Less well understood are the rapid current changes in a moving mount, or active computer.
If you have a long wire length, a local capacitor may help.

If it all sounds complicated, then go for the easy solution.
Keep the 12V power supply, or battery, local to the mount. That avoids voltage drop worries.
That is the approach I have always taken.

HTH, David.

 

[CraigT82]

Plug your info into here to check what size cable you need (but I think you'll need at least 2.5mm2 cable):

https://www.12voltplanet.co.uk/voltage-drop-calculator.html

Something like this would probably do, along with the connectors shown above by fifeskies

https://marine-electricals.co.uk/product/tinned-twin-round-cable-2-x-2-5mm/?utm_source=google&utm_medium=cpc&utm_term=4972&gclid=Cj0KCQjw5ZSWBhCVARIsALERCvxCq638yF2NZ2g_lwBokdvKjoqt_Btx4Br1dtHEuyue02E_Ymd-pvsaArRWEALw_wcB

Add in a bit of heatshrink and Bob's yer uncle

 

 

Edited July 6, 2022 by CraigT82
wrong link

[fifeskies]

I should have added,  I use a big 13.8v linear supply, so can easily cope with a voltage drop of a volt or so out to the mount.

If your supply only delivers a flat 12v , as CraigT82 has mentioned above you may need to use heavier gauge cable.

Most of the re-wirable adapters can be persuaded to take up to 2.5mm stranded cable, but check the exact ones you are considering , they vary in quality.

Crimped termination sleeves to the cable ends can help to fit them into the adapters.

Edited July 6, 2022 by fifeskies

[bosun21]

On 05/07/2022 at 16:01, DaveL59 said:

losses in the cable over that length will always be an issue with this type of plug as they aren't really designed to take heavy gauge wire

The heavier gauge that the wire is the less the losses incurred.

[Ouroboros]

Oh, what a lovely lot of replies. Thanks so much everyone!
I’ll respond to some  of your comments below. 

[Ouroboros]

On 05/07/2022 at 15:21, SthBohemia said:

Fabricate the cord from heavy duty speaker cable or run the mains to the PSU placed close to the mount. I fabricated  a cord using speaker wire running a similar distance to yourself, but used inferior quality wire. Just compensated by adjusting the switched power supply (12v@8A) for a Skywatcher EQ6 up to 13.5 volts. Must make a better cable... Someday...

This might be what I do. I use 10 metres of 2-core mains lamp-cable (from BMQ) to supply my mount from a 13.8V supply. That works well. The mount reports a healthy +13V supply. 

[Ouroboros]

19 hours ago, Budgie1 said:

If you're worried about dew with a mains extension then a waterproof extension or normal extension lead into a Dri-Box should do the trick.  

I see this is a workable solution. In fact taking mains to the mount is what I ended up doing temporarily in a sort of improvised way.

I prefer not to take mains outside if I can. But I like your thinking. 

[Ouroboros]

3 hours ago, fifeskies said:

rewirable adapters allow you to easily make up any length of high current DC cable without having to solder large cables onto small fiddly tabs.

I use 1mm 2-core rubber cable (or 2-core 0.75mm for shorter runs)

It can be a good idea to also use an inline fuse.

 

I’ve seen those connectors. You reckon they’re OK do you?  I don’t like that they look open at the back end. There won’t be any shock hazard but it’s still open to damp.  I might get some though just to play with. 

[Nugs]

1 minute ago, Ouroboros said:

I’ve seen those connectors. You reckon they’re OK do you?  I don’t like that they look open at the back end. There won’t be any shock hazard but it’s still open to damp.  I might get some though just to play with. 

A tiny dab of silicone sealant is your friend. 👍

[Ouroboros]

3 hours ago, Carbon Brush said:

A couple of comments to get the problem into perspective.

A 1mmsq cross section copper wire has about 180milliohms resistance at 20C.
You can easily recalculate for thinner/thicker wires.
Ohms law gives you 0.18V drop at 1A, or 0.9V at 5A.

On a -10C night, the number above becomes 160mohms.
For solar observers, at 40C it is more like 190mohms.

The above calulation relates only to the wire. Not accounting for resistance in assorted connections.

A further consideration is that the load (whether mount computer or dew heater) does not take constant current.

An easily understood example being a dew heater turning on/off as the power is adjusted.
The heater might take 5A. But when running 20% power, it may cycle 1sec ON and 4sec OFF.
When considering power supply capability and cable voltage drop, it is the ON figure that you must use.

Less well understood are the rapid current changes in a moving mount, or active computer.
If you have a long wire length, a local capacitor may help.

If it all sounds complicated, then go for the easy solution.
Keep the 12V power supply, or battery, local to the mount. That avoids voltage drop worries.
That is the approach I have always taken.

HTH, David.

That’s the way to do it. Do the maths!  As I mentioned above, I’ve already showed this works with some decent domestic mains flex.

I might replace my 12V supply with another 13.8V one too.   I think the ASIair is happy with a bit more than 12V. 

Edited July 6, 2022 by Ouroboros

[DaveL59]

44 minutes ago, Ouroboros said:

I see this is a workable solution. In fact taking mains to the mount is what I ended up doing temporarily in a sort of improvised way.

I prefer not to take mains outside if I can. But I like your thinking. 

make sure its on an RCD protected circuit and be cautious handling when wet 🙂 

I have made use of those DIY connectors myself, for CCTV gear and they do work fine. Some dielectric grease would prevent moisture tho if you get that on your fingers when setting up don't go handling any of your expensive glass or sensors as its 'fun' to clean off after. unless you like the soft focus views of course, like vasolene on a filter effect 😉 

Edited July 6, 2022 by DaveL59

[fifeskies]

32 minutes ago, Ouroboros said:

I’ve seen those connectors. You reckon they’re OK do you?  I don’t like that they look open at the back end. There won’t be any shock hazard but it’s still open to damp.  I might get some though just to play with. 

Among other ways to seal these other than grease are :-

 

 adhesive lined heatshrink

(But this makes for a very rigid connection)

 

Or self amalgamating tape

(This forms a flexible rubber like sealed cover, but remains slightly sticky for a while)

[SthBohemia]

Thought I might show a pic of the PSU I use outdoors sitting on its raincoat. A few bits of 'tin' plate, Meccano and a few screws, voila 🙂

[CraigT82]

47 minutes ago, SthBohemia said:

Thought I might show a pic of the PSU I use outdoors sitting on its raincoat. A few bits of 'tin' plate, Meccano and a few screws, voila 🙂

I really hope that casing is earthed?! 

[SthBohemia]

22 minutes ago, CraigT82 said:

I really hope that casing is earthed?! 

Double earthed Craig! It sits on the damp ground AND does have an earthed wire!! I am getting careful in my old age 🙂