Combined power supply

[freiform]

Hi,

I wanted to get rid of the individual power supplies for the respective devices,  i.e. mount, cameras, UBS-hub, focuser, etc. This is intended for use where mains electricity is available, read: at home ;).

I thought about getting a small PSU, which would provide both, 5 and 12V out of the box. Fore the more exotic voltages like the 7.4V for the Canon DSLR, I wanted to use small, LM2596-based boards, which are available for very few payment units [1].

All put into a neat little case with some robust connectors (maybe XLR, although cinch might do the job just fine), and I'm all set.

Do any of you have any thoughts on the matter, anything I should beware of or could improve on?

Thanks for any input.

 

[1] https://www.amazon.de/dp/B009P04YTO

[pete_l]

Sounds like a plan. I have something similar but limited to 12V and 5V.

I'd suggest having a combined Volt/Amp meter on the output from the battery (before it splits to the various SMPSs) so you can keep an eye on the total current draw and battery status.

Make sure that all the connectors for the different voltages are NOT interchangable and can't be plugged in with reverse polarity!

[Dr_Ju_ju]

As I have a 650Watt PC power supply adjacent to my mount, I use it to supply 12\5v rails and use Bucky converters to drive heaters cameras etc....

[hughgilhespie]

Hi,

I would be careful about using the cheap buck converters to supply power to expensive things like cameras. If you use these, for a few extra 'payment units' you can add fuses and crowbar protection to the low voltage outputs. This will protect the expensive equipment in the event of a failure. This is a simple circuit that works well.

Regards, Hugh

 

 

[freiform]

Thank you for your replies. 

As this supply will run of mains, a display of V/A is not required. Having some sort of protection build in is a good idea, though. I'll keep you posted!

Sven

[cjdawson]

If you take a look through my past posts, you'll see that I've done just that.  What I built is a three stage system.

 

1. Battery box.

2. Dew heater control box

3. Telescope power distribution box.

 

Here's what each box does.

The Battery box

4 * 12v Marine auto sockets.  (similar to the one you get in cars)

4 * 2 amp USB sockets (2 units each containing 2 usb charging ports) (can be swtiched off)

XLR Socket - allows me to plug the Dew heater box directly into the 12v of the power box.

300W Inverter inside the box.

Jump starting points, used to charge the battery with a battery charger.

XT-60 socket panel mounted.   This will let me add a second battery in parrellel later on, so that I can get more amp hours.

Battery charge indicator (on a switch)

Volt meter and ammeter (on a switch)

Lots of fuses to protect everything.

 

On it's own this box can also serve as a camping power supply.  The box has wheels and a collapse able handle so it's easy to move the heavy battery around.

 

The Dew heater control box.

This box contains two Pulse Width Modulator circuits, one for each of my dew heater elements.

It also has a 12v-5v DC-DC converter, so that I can run things on my scope that need 5V.

This plugs into the battery box with an XLR Socket and a cable that I made up.

The outputs from the 5V, 12V and each PWM are directed through a 9-pin D-Sub port, and cable to the Telescope distribution box.

I'm soon going to be adding a 12V to 8V DC-DC converter to be able to run my DSLR.

 

 

The Telescope distribution box.

This takes the input from A 9-pin D-Sub port.

2 of the wires are used for dew band 1.

2 more for dew band 2.

1 wire is common 0V (ground)

1 wire is 12V

1 wire is 5V

1 wire will be 8V

1 Wire spare.

 

The 12V wire, splits into 3, each supplying a seperate 12v DC Socket. (each has it's own 2Amp fuse)

The dew bands have their own sockets of a different kind.  I used 3.5mm Mono Jacks as I didn't like the RCA connectors (had them fall out on me in the past)

The 5v goes to a different sized DC Socket.

And I have yet to wire up the 8V.

 

I've used this setup a number of times without any issues, it's very neat as there are very few wires running from the battery box to the scope, two in total, 12V cable to the dew box and a serial cable for the scope power.

The whole lot locks together so there is little chance of accidentally knocking the power out.

 

[MarkyD]

I built mine to control dew heaters and mirror fan, supply 14V to the Mount, house a usb hub and supply oulets for 12V and 5V.  It's all contained in a Pelican box with Touch screen LCD screen for info and control.  It also has an Intervalometer programmed into it to control the DLSR.  All controlled by an Arduino Mega2560

Final LCD

 

LCD Screen in the making

 

USB, power sockets (3 empty holes), shutter release socket and fan connector.  The mount power and dew heater connections are at the rear of the case

 

Internals

 

[1CM69]

On 8/4/2016 at 21:33, hughgilhespie said:

Hi,

I would be careful about using the cheap buck converters to supply power to expensive things like cameras. If you use these, for a few extra 'payment units' you can add fuses and crowbar protection to the low voltage outputs. This will protect the expensive equipment in the event of a failure. This is a simple circuit that works well.

Regards, Hugh

 

 

Hi,

an old thread I know but I am struggling to build my own crowbar circuit.

My power pack outputs 13.8VDC and if all my connected equipment is running at the same time, it'll draw 6.65A.

I wish to limit over voltage to 14v.

Could you help with the formulas so I could then order the components?

Regards..,

[hughgilhespie]

Hi,

Have a look at the datasheet for the LM431 Adjustable Zener, http://www.ti.com/lit/ds/symlink/lm431.pdf. This shows the calculation you need on page 16.

My version was designed to limit the output voltage to 5.2 volts. I used a 10k potentiometer (variable resistor) with the wiper connected to pin 2 of the LM431 and the outer connections to the +5V and ground. This replaced R1 and R2. That way I could adjust the output voltage to the value I wanted.

No guarantees - I am NOT an expert but for your 14 volt design I suggest that you increase the values for R3 and R4 to about 1200 ohms. A 10k pot will be OK for R1 + R2.

Hope this helps, 

Regards, Hugh

[1CM69]

38 minutes ago, hughgilhespie said:

Hi,

Have a look at the datasheet for the LM431 Adjustable Zener, http://www.ti.com/lit/ds/symlink/lm431.pdf. This shows the calculation you need on page 16.

My version was designed to limit the output voltage to 5.2 volts. I used a 10k potentiometer (variable resistor) with the wiper connected to pin 2 of the LM431 and the outer connections to the +5V and ground. This replaced R1 and R2. That way I could adjust the output voltage to the value I wanted.

No guarantees - I am NOT an expert but for your 14 volt design I suggest that you increase the values for R3 and R4 to about 1200 ohms. A 10k pot will be OK for R1 + R2.

Hope this helps, 

Regards, Hugh

Thanks for the info. ?

[hughgilhespie]

Hi,

One other thing I forgot to say. For testing/calibrating the circuit, I removed the fuse and connected a 6 volt bulb in its place. For your 14 volt circuit a 12 volt bulb would be needed, ideally a bulb that takes a similar current to your normal operating current, e.g. if you want to protect a 3 amp supply then a 12 volt 36 watt bulb would be perfect. You will also need a variable bench power supply connected to the input. Then all you have to do is connect a voltmeter across the input and adjust the potentiometer until the bulb lights up when the input is at 14 volts. If you don't have access to a variable power supply, I suggest connecting the input to a 12 volt battery charger, this will be around 14.5 volts, then adjust the pot until the bulb just lights up. The pot can be a trim pot type but needs to be a decent quality one.

Regards, Hugh

[1CM69]

5 minutes ago, hughgilhespie said:

Hi,

One other thing I forgot to say. For testing/calibrating the circuit, I removed the fuse and connected a 6 volt bulb in its place. For your 14 volt circuit a 12 volt bulb would be needed, ideally a bulb that takes a similar current to your normal operating current, e.g. if you want to protect a 3 amp supply then a 12 volt 36 watt bulb would be perfect. You will also need a variable bench power supply connected to the input. Then all you have to do is connect a voltmeter across the input and adjust the potentiometer until the bulb lights up when the input is at 14 volts. If you don't have access to a variable power supply, I suggest connecting the input to a 12 volt battery charger, this will be around 14.5 volts, then adjust the pot until the bulb just lights up. The pot can be a trim pot type but needs to be a decent quality one.

Regards, Hugh

Superb, thanks.