Powering Wifi adapter

[Chris]

Hello,

Have just ordered and have a question. Can I power a Wifi repeater from the opensprinkler box?

I understand most wifi repeaters have a USB connector for powering. Can this 5v DC come from the inbuilt switching regulator.

The only power source I have at the place where I want to install it is the 24vac line.

Thanks in Advance.

[Ray]

Hi Chris,

Good question. The answer is yes, and I've just experimented with it last week. You need two modifications:

1) solder an extra 1ohm resistor in parallel with Rsc (the current limiting resistor for 34063 switching regulator), this is to increase the current output of the +5V line. On OpenSprinkler 1.3 and 1.4, you will find a resistor slot parallel to Rsc, and that slot is exactly designed for this purpose.

2) get a USB Male B to Female A converter, such as this one:

http://www.amazon.com/USB-Type-Female-Male-Adapter/dp/B000AA2SMS

and plug it into OpenSprinkler's USB port. Then you can plug your WiFi adapter's USB power cable to the converter and it should work.

I will soon write a post about this. If you can't figure out how to make it work, just wait for the post.

[garygid]

The WINCE2001 labels its power port as 5v and 1 amp.
Any idea how much current this adapter really requires?

Thanks for your continued great work, Gary

[Dave Hylands]

Hi,

On Thu, Oct 4, 2012 at 8:42 AM, garygid <hairy...@gmail.com> wrote:
> The WINCE2001 labels its power port as 5v and 1 amp.
> Any idea how much current this adapter really requires?

Many wifi adapters really require that much current. I've worked with
some non-USB ones that would instantaneously draw 2A.

Steady state, it will use much less, but while transmitting, it will
probably draw close to its stated current.

--
Dave Hylands
Shuswap, BC, Canada
http://www.davehylands.com

[Ray]

I measured WINCE2001 draws about 350mA-400mA during operation (the OpenSprinkler itself draws about 160mA). It is designed to work with a standard desktop USB port, so I assume it shouldn't draw more than 500mA. As Dave said, the actual current draw depends on the transmission power etc. In any case, the 34063 regulator can output a maximum of 1.5A. The output current can be adjusted by changing the Rsc resistor. Rsc is 1ohm by default, and that produces a maximum of 0.33/1 = 330mA output current (according to 34063 datasheet). Connecting another 1ohm resistor in parallel will double the current output, and so on. Of course you should leave some safety margin. For example, if the circuit draws 500mA in total, the current capacity should be at least 800mA to 1A. So it's probably a better idea to have three 1ohm resistors connected in parallel in order to have 1A output current.

[Ray]

I've written a blog post about this. Check it out at:

http://rayshobby.net/?p=4233