Multiple/adjustable power supply for scope & camera

[Crushellon (Tim)]

Spent last night building a power supply for my neq6/mirror fan/camera. I wanted to stop using the little internal battery in my 550d but without having to have an extra external battery to lug around so I made a power supply that you connect to a 12v battery and outputs 2x 12v plugs and a third plug with adjustable voltage to accomodate my camera which runs at 7.2v. It has a voltmeter and ammeter for the whole system and a voltmeter for the adjustable voltage plug with seperate on/off switches for the two voltages. Pretty happy with it. It's small enough and light enough that I will be able to put some sticky Velcro on it and have it on the side of the neq6. It will tidy up the power cables significantly and looks pretty professional.

[mikerr (Michael)]

Very well thought out and executed Tim.
What is the maximum current available at the various voltages?
Did you document the build? I, and I'm sure others, would be interested in the parts list and build details.

Thanks for sharing

Michael

[OffGrid (Steve)]

Congrats Tim, that does look pro in my opinion.
I cannot see how you connect to your battery so here is how I do mine.
My batteries are multitasking between astro and camping and also taken to Girl Guide jamborees so they need to be bullet proof and simple to connect.
So I chose to make up short Anderson fused connecting tails that are glued to the top of the batteries as per pics.
This means when I am not around, things such as chargers, loads and solar panels can be connected without getting the polarity wrong, even in the dark.

[Crushellon (Tim)]

Originally Posted by mikerr

Very well thought out and executed Tim.
What is the maximum current available at the various voltages?
Did you document the build? I, and I'm sure others, would be interested in the parts list and build details.

Thanks for sharing

Michael

Thanks Not sure on the max current because the voltmeters were just old ebay purchases that I had lying around, I wouldn't push them past 5A without knowing what they are capable of. The 12v side of things is bottle necked by whatever voltmeter you use, which can easily be pushed higher by getting a higher capacity meter. The variable side however is limited to 1.5A output by the DC/DC converter (AA0236 from jaycar).

As far as parts lists everything can be interchanged with any old switches and plugs you have lying around, except for the AA0236 (6-28V DC/3-15V DC converter). The whole build revolved around a voltmeter for input - power out/power to the DC converter - and a voltmeter after DC conversion.

Originally Posted by OffGrid

Congrats Tim, that does look pro in my opinion.
I cannot see how you connect to your battery so here is how I do mine.
My batteries are multitasking between astro and camping and also taken to Girl Guide jamborees so they need to be bullet proof and simple to connect.
So I chose to make up short Anderson fused connecting tails that are glued to the top of the batteries as per pics.
This means when I am not around, things such as chargers, loads and solar panels can be connected without getting the polarity wrong, even in the dark.

Thanks I've just got alligator clips for now. I'm using car batteries at the moment, I'll save making up a battery box for when I get a nice deep cycle battery. Yours look good.

Tim.

[OzEclipse (Joe Cali)]

Originally Posted by Crushellon

Thanks Not sure on the max current because the voltmeters were just old ebay purchases that I had lying around, I wouldn't push them past 5A without knowing what they are capable of. The 12v side of things is bottle necked by whatever voltmeter you use, which can easily be pushed higher by getting a higher capacity meter.

A voltmeter is a high impedance device running in parallel with the driver current. You can drive any amperage through the car battery side and the voltmeter (any voltmeter) won't care. It's only measuring volts by measuring current passing through a BIG resistor, the high current isn't passing through it.

I have made a couple of portable power supplies using LM2596 buck converter circuits modules from ebay which might be what you are referring to. You can buy them in a number of layouts. The more they have, the more you pay. The one in the picture below can be purchased for $4-$6 ea.

You don't need to know much about electronics at all to hook them up. Attach a DC supply voltage in one end, they have a built in meter for measuring output voltage, potentiometer for adjusting the variable output, they supply up to 3A, and a USB outlet as a bonus. They are 90+% efficient on the conversion depending on the voltage used. Put a decent voltmeter on the output. I have found that the meters are out by a few tenths of a volt.

I've used mine for building two supplies, one for generating voltages to run devices from penlight batteries and the other from D cells. I use the penlight version to take on planes and the D cell to run my iEQ45 for short periods - up to an hour or two if I have to carry it away from the car. The iEQ45 tracks at 200mA.


Wide Input voltage: 4.5-40V.
● Output Voltage: 1.25-37V (Adjustable).
● Output current: rated current 2A, 3A MAX ( Heat-sink Needed).
● If you need its output power greater than 2A/10W, please add with heat-sink.
● Conversion efficiency: Up to 92% (output voltage higher, the higher the efficiency).
● Switching Frequency: 150KHz.
● Rectifier: Non-Synchronous Rectification.
● Module Properties: Non-isolated step-down module (buck).
● Short circuit protection: current limiting, since the recovery.
● Operating temperature: Industrial grade (-40 to +85 ) (output power 10W or less).
● Full load temperature rise: 40.
● Load regulation: ± 0.5%
● Voltage regulation: ± 2.5%
● Dynamic response speed: 5% 200uS.

Joe