Does this exist? (12v to PWM control of 2 USB dew heaters)

[AstroViking (Steve)]

Hi all,

I had the controller on my USB-powered (5v/2.4A) dew heater decide to self-immolate last night.

I've been looking around and all I can find are dew heater controllers that drive 12v heater straps. (I did find the Jaycar project but it doesn't look to provide enough current to drive 2 straps, and there were comments about the code for the Arduino being unreliable. I also saw ChrisV's project here, but that drives 12v heater straps.)

So I'm asking here if anyone knows of a controller that can take a 12v input and has some form of temperature / power output control to feed 2 USB dew straps. Ideally, it would be small enough that it fits somewhere on the mount, and also has some form of smarts (ie, change power output depending on environmental temperature and humidity.)

Many thanks,
V

[OICURMT]

Any Buck Converter can do the job for you... though there are not "smart".

[AstroViking (Steve)]

That might be a good starting point - drop the 12v down to 5v and feed that into some sort of controller / PWM circuit before sending that out to the heater straps...

I was hoping not to have to design anything as I haven't touched circuit design and the like since I was at Uni (sometime last century). (I'm OK with assembling something, as I can drive a soldering iron and follow instructions.)

Cheers,
V.

[ChrisV (Chris)]

No reason why you can't run my controller at 5V, although it might be a bit of overkill if all you want is manual control of heating.

Also, you could run into trouble because a 5V @ 2.4A power source is only a bit over 10W. This might not be enough for many heater applications e.g. heating a big chunk of glass or having multiple things to heat.

I have also used aliexpress usb heater straps with my device as they are so cheap. Just replaced the wiring with 4-core cable to add a temperature sensor.

[ChrisV (Chris)]

Or on ebay, search

5V-16V 10A PWM DC Motor Speed Controller Regulator LED Dimmer Speed Control .A2

This should give simple PWM control of 5V

[AstroViking (Steve)]

Thanks Chris!

My 'scope is a SW72ED, so not a massive chunk of glass by any means.

Using our search terms, I found a swag of those PWM dimmers, and for $5 each, I can't really go wrong. With some careful work I might even be able to fit them into my existing 12v distribution box. (If not, another project box from Jaycar is not expensive.)

Many thanks again!

Cheers,
V.

[Leo.G (Leo)]

I tend to hit Aliexpress in preference to Jaycar, same quality items at less than half the price. Unless I need it in a hurry.
When Jaycar first opened they were in Hurstville (NSW) around the corner from where I lived. They had amazing stuff at great prices and even offered me a job, I was studying electronics engineering at the time and all staff had a high level of knowledge of electronics. Then they opened Bankstown, then got big and their products lost a lot of the quality while pricing jumped significantly. I tend to avoid them now.

[Boorkus (Boorkus)]

A basic PWM controller (they're all over eBay) is all that's needed. The smarts will be more complicated, you may be better off learning Arduino and coding it in an Arduino. The Arduino can also use hardware timers to trigger the PWM and drive a MOSFET to drive the heater strap.

[AstroViking (Steve)]

Thanks guys. I'll keep plodding along and see what I can come up with. When I do have something working I'll post updates here.

Cheers,
V.

[AstroViking (Steve)]

Finally finished the thing. It took longer than I anticipated due to me getting too small a project box to put everything inside.

It's certainly not small (like the Pegasus Astro and similar devices), but it has a row of 12v outlets on one side and two variable output PWM controllers to drive my USB dew heaters on the other.

V.