Does anyone know of any DIY Powerbox plans available?

[dazzystar]

Hi All,

Looking to build my own powerbox. Does anyone know of any DIY plans that may be available? Something similar to the PPB.

Cheers

Daz

[Clarkey]

I don't have plans but I have just built my owner 'powerbox'. Nothing too fancy, 4 12v outputs, 4 USB 5v outputs an two variable dew heater outputs, all from a 12v supply 10A total. In theory it could be customized to suit. Probably cost about £50. Yes, its slightly bigger and less elegant than a Pegasus, but I'm tight😄

Happy to share photos. (Sparkys look away)

Edited February 4, 2022 by Clarkey

[dazzystar]

13 hours ago, Clarkey said:

I don't have plans but I have just built my owner 'powerbox'. Nothing too fancy, 4 12v outputs, 4 USB 5v outputs an two variable dew heater outputs, all from a 12v supply 10A total. In theory it could be customized to suit. Probably cost about £50. Yes, its slightly bigger and less elegant than a Pegasus, but I'm tight😄

Happy to share photos. (Sparkys look away)

Yes please. Love to have a look. If you have a circuit diagram too?

[Clarkey]

Circuit diagram!!??🤣 Sorry - I wouldn't have a clue! Here are some pictures - as I said no award for neatness. Basically all the bits are from ebay / amazon. Standard RCA sockets for the dew heaters, 12V usb sockets, 5A PWM circuit boards and 5.5mm x 2.1mm. They are all fed directly from a 12V DC cigarette plug via the quick connector boxes as it is a bit easier than soldering them all. The box is an external junction box. (I can send you the amazon links if you want)

I have not tried the 5A PWM yet - previously I used 10A units, so I don't know about reliability of these yet. The 10A have built in heat sinks which are missing from these. However, as I am rarely drawing more than 1 amp they should be OK.

There probably should be some more fusing built in other than the 10A fuse on the feed, but that is a personal think. Any short on the 12V outputs will instantly blow the main fuse and the PWM will blow above 5A (or a short) so I am willing to take the risk.

As I am running on a 13.8V regulated supply the voltage drop on the 0.75mm2 cable is not an issue. If running from a battery supply you probably want to use a 1.5mm core on the main supply cable so the voltage drop is not too much.

Hope this helps.

I'm sure there will be more expert electricians on a bit pointing out all the defects! But I have made a couple of these and not had any problems (yet).

 

[dazzystar]

42 minutes ago, Clarkey said:

Circuit diagram!!??🤣 Sorry - I wouldn't have a clue! Here are some pictures - as I said no award for neatness. Basically all the bits are from ebay / amazon. Standard RCA sockets for the dew heaters, 12V usb sockets, 5A PWM circuit boards and 5.5mm x 2.1mm. They are all fed directly from a 12V DC cigarette plug via the quick connector boxes as it is a bit easier than soldering them all. The box is an external junction box. (I can send you the amazon links if you want)

I have not tried the 5A PWM yet - previously I used 10A units, so I don't know about reliability of these yet. The 10A have built in heat sinks which are missing from these. However, as I am rarely drawing more than 1 amp they should be OK.

There probably should be some more fusing built in other than the 10A fuse on the feed, but that is a personal think. Any short on the 12V outputs will instantly blow the main fuse and the PWM will blow above 5A (or a short) so I am willing to take the risk.

As I am running on a 13.8V regulated supply the voltage drop on the 0.75mm2 cable is not an issue. If running from a battery supply you probably want to use a 1.5mm core on the main supply cable so the voltage drop is not too much.

Hope this helps.

I'm sure there will be more expert electricians on a bit pointing out all the defects! But I have made a couple of these and not had any problems (yet).

 

Great!

Where and what model number are the PWM dew heater modules? I'd use a buck converter for the 5V USB lines on mine.

[Clarkey]

17 minutes ago, dazzystar said:

Where and what model number are the PWM dew heater modules

The are the ones I used this time but there are plenty to choose from:

Gebildet 3pcs DC 5V-35V 5A Mini DC Motor PWM Speed Controller, 6V 12V 24V Variable Voltage Regulator Dimmer Governor Switching Build with LED Indicator : Amazon.co.uk: Business, Industry & Science

 

[Richard Wesson]

I would like to create something like this. I have sepearte dew heater ontroller, power distirbution box, and USB 3 hub. However, I would like to combine the 3 elements into one box. Combining the 3 elements probably not that difficult, but I was wondering how I could implement this with soft con trol for the dew heater outputs? Anybody any thoughts? 

[Clarkey]

The PWM are variable power for dew heaters.

[Carbon Brush]

Inadvertent enter key press. Post deleted.

Edited February 5, 2022 by Carbon Brush
Inadvertent enter key press

[Richard Wesson]

10 minutes ago, Clarkey said:

The PWM are variable power for dew heaters.

That is what I currently use, but  wondered if there was a way to implement dew heater control with software as in the pegassus powerbox?

[Carbon Brush]

Some of the low cost motor drives will accept a 0V/5V analogue input, instead of using the potentiometer.
This facility is described in very few of these drives, but present without being documented. You buy and try.
However, you then need a control computer or whatever with analogue output!

An alternative is a different board with I2C or SPI interface to Arduino/Raspi type boxes.
These often being suited to stepper motors rather than brushed DC. So choose carefully. Then you have to write the software.

Twiddling the knobs, or buying a commercial product are the only easy options.🤨

[Richard Wesson]

6 hours ago, Carbon Brush said:

Some of the low cost motor drives will accept a 0V/5V analogue input, instead of using the potentiometer.
This facility is described in very few of these drives, but present without being documented. You buy and try.
However, you then need a control computer or whatever with analogue output!

An alternative is a different board with I2C or SPI interface to Arduino/Raspi type boxes.
These often being suited to stepper motors rather than brushed DC. So choose carefully. Then you have to write the software.

Twiddling the knobs, or buying a commercial product are the only easy options.🤨

Not really interested in motor control - more control of dew heater power via software. I believe it has been implemented in indi, but need to find a way to interface. I guess an arduino solution may work, but would need circuit for this. 

[dazzystar]

If you find a circuit, let me know!

[Carbon Brush]

It is just that motor controllers can be used and they are available ready built.
They have power transistors switching on/off in a controlled, timed, manner.
Some even have short circuit protection - very useful with 'lash up' heater looms relying on DIY soldering cables and RCA plugs.
That is the functionality you seek in a heater control.

As it happens a heater control can switch at intervals of seconds because of thermal lag. Motor control is the (sometimes sub) millisecond region.
The principle is the same. Turn a transistor on/off with a known ratio to obtain the desired proportion of full power.
You have to establish drive suitability for yourself because the specification (using the term very loosely) provided on Amazon stuff from China is a joke.
But, if the motor drive will accept a logic level signal from your computer, this makes life easier.

You can drive a (Raspi/Arduino/whatever) GPIO ports on/off at intervals of a second or two. Feed this into a suitable motor drive.
In basic form it is a fixed on/off. If you want to make adaptive/clever, put thermistors into analogue inputs and use software to modify the on/off timings.
A further clever software touch is to ensure the outpts are sequenced to ensure they aren't all on at the same time.
This restricts maximum load on the PSU.

Alternatively, if you don't want to use motor drive boards, the same signals can feed (but not directly) into suitable power transistors. Then you have the hardware side of a heater control.
This control is doable for a competent hobbyist. A hobbyist who is happy to lay out then manufacture a PCB.
Tag strip will easily turn into rats nest and veroboard is not a good substrate for the application.

If you need a circuit drawing out for self build with Raspi, power transsitors etc. the chances are there will be build errors ⚡🥴and you won't be able to fault find.
Sorry if this sounds brutal. But it is my observation from a lifetime of electronics design, test and repair.

Twiddling the knobs, or buying a commercial product are the only easy options.

@Clarkey has wisely chosen an assembled power stage and proprietary 12V/5V convertors. Why re-invent the wheel?
This leaves free him to concentrate on the box wiring and construction.
If I was building a one-off for my own use, that is the approach I would take.

HTH, David.

 

 

[dazzystar]

I don't have a heated dew strap yet but am sure I'll need one for me ST102 at some stage. I thought these just ran off 12v and were either on or off. Are the pots on the motor controllers varying the voltage to the heater?

[Clarkey]

10 hours ago, dazzystar said:

Are the pots on the motor controllers varying the voltage to the heater?

They don't vary the voltage but pulse power to them for more or less of time. For low power dew heaters you can just have on or off, but this gives a bit more control

[Len1257]

For a full blown Dew Controller see Robert Browns Dew Controller

I built one and then decided it was too big to be practical for my use. I now use a 3D printed power distribution box and a seperate dew control box using the pwm modules from the bay. Simple and easy, just crank the knob to suit the conditions.

[Carbon Brush]

The Robert Browns is very good. both functionally, and as an example of how building is not that easy.
It makes you appreciate just how many of the commercially built devices we buy are such a bargain.

 

[scotty38]

13 minutes ago, Carbon Brush said:

The Robert Browns is very good. both functionally, and as an example of how building is not that easy.
It makes you appreciate just how many of the commercially built devices we buy are such a bargain.

 

I would have to agree. My background is in electronics and I have a load of kit at home including the likes of oscilloscopes BUT I don't need or want another hobby on top of this one so I bite the bullet and buy the Pegasus type commercial offerings too 🙂

[adyj1]

I appreciate this thread is about a power box, but if you want manual/ASCOM-controlled dew strap control you can do a lot worse than the Lynx Astro controllers from FLO. I've got the 2-port version where you have one heat setting for both ports, but the 4-port version allows individual control on all ports. £69 and £99 respectively. No fancy external temperature monitoring, but that would cost a lot more. 

[dazzystar]

I built Robert Brown's autofocuser...or a slightly modified version of it...was a tad complicated for me but.....