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1  Using Arduino / Project Guidance / Re: Is this possible without relays on: October 20, 2012, 08:30:35 pm
You can use a transistor, a mosfet, or opto-isolator to simulate button press. But I agree that no voltage reading between the two wires is strange.
2  Using Arduino / Project Guidance / Re: Power from 24VAC on: October 20, 2012, 08:13:39 pm
If power consumption is not an issue, there are a variety of simple ways to drop 24V to 12V. Zener diode, 7812 or other linear regulators... But if the circuit is drawing sizable amount current (like mine draws about 180mA current), then (33-12)*0.18 = 3.78 Watt power will be wasted. Note that the 33VDC comes from rectifying 24VAC. In fact, there will be more because the 12V to 5V conversion will waste another (12-5)*0.18 = 1.26 Watt. That's a total of 5 Watt. So in this case switching regulator is more efficient.
3  Using Arduino / Project Guidance / Re: Power from 24VAC on: October 20, 2012, 07:29:00 pm
Depends on how much current your circuit draws. If it's small, like tens of milliamps, a zener diode is good enough and won't waste too much power. If it's something like hundreds of milliamps, a switching regulator is better since it's much more efficient. A half-wave rectifier (i.e. single diode) plus big cap is sometimes good enough for AC-DC conversion.

I used a MC34063 switching regulator for my sprinkler controller circuit:
https://raw.github.com/rayshobby/opensprinkler/master/OpenSprinkler%20Controller/hardware/v1.4/OpenSprinkler_v14.png
look at the "power supply" section on the top-left corner.
4  Using Arduino / Project Guidance / Re: Low Power Arduino on: October 20, 2012, 10:35:59 am
Battery powered option is useful if your sprinkler valves are battery operated too (based on latching solenoids):
http://rayshobby.net/blog/?p=18
You can then run the timer on battery and place it in your garden without external power.

Otherwise I don't see a strong reason to put Arduino to sleep, since your sprinkler valves are probably drawing more power than Arduino.
5  Topics / E-Textiles and Craft / SquareWear: a new open-source wearable electronics board on: October 18, 2012, 11:36:46 pm
Hi, I just finished working on a controller board I built myself for wearable electronics projects. It's called SquareWear. I thought about posting it here in case someone may find it interesting. I designed it mainly as a low-cost solution for entry-level projects and wearable electronics workshops at schools. It has a built-in USB port (used for programming the microcontroller, creating USB serial communication, and charging battery), HID bootloader, power sink pins (suitable for driving high-current load), li-po charger, on-board LED and general-purpose push-button. Basically I've pictured it as a sewable microcontroller board that can get someone started right away -- no external programmer and no driver installation needed.

Here is an introduction video:



Find out more at http://www.sqrwear.com. Thanks.
6  Topics / Home Automation and Networked Objects / Re: Remote controlled power sockets on: July 01, 2012, 09:04:25 am
Ok, finally I found a simple and general method to work with basically any off-the-shelf remote controlled power sockets. The idea is to first use an RF receiver + sound card + audio recording software to sniff the remote control signals, then 'play it back' using an Arduino + RF transmitter to simulate the remote control. I wrote a blog post about this method, which you can find at:
http://rayshobby.net/?p=3381
It also includes a demo of Internet-based control of devices using an existing OpenSprinkler board.
Hope this is useful smiley



-Ray

7  Topics / Home Automation and Networked Objects / Re: Arduino and Sprinkler System Solenoids on: May 13, 2012, 11:45:54 am
I agree using a relay is simple, but I prefer using triacs because they much smaller in size and significantly cheaper. They are easy to use (connect them just like standard transistors) for switching low-voltage (like 24V) AC power. For high-voltage switching I would prefer using a relay as it decouples the control circuit with the load circuit and is thus safer.
8  Topics / Home Automation and Networked Objects / Re: Arduino and Sprinkler System Solenoids on: May 11, 2012, 04:24:52 pm
Check out our OpenSprinkler project:
http://opensprinkler.com
9  Topics / Home Automation and Networked Objects / Re: Remote controlled power sockets on: May 11, 2012, 04:16:22 pm
I was recently experimenting with remote controlled power sockets, and here is a post about how to do it with an Arduino and an RF transmitter:
http://rayshobby.net/?p=2427

and a video:
http://www.youtube.com/watch?feature=player_embedded&v=CbX17sxbk68
10  Using Arduino / General Electronics / Re: General Idea for Sprinkler System Controller on: April 11, 2012, 11:20:34 pm
Hi, as dc42 noted, the Ethernet controller consumes about 180mA current. Including other components, the total current draw is probably around 200mA. If you use a linear regulator, the power wasted on the voltage drop is roughly (24-5)V * 0.2A = 3.8W, which is somewhat significant. The reason I used a switching regulator in the design of OpenSprinkler is exactly to reduce the power waste, because switching regulators are more efficient.
11  Topics / Home Automation and Networked Objects / OpenSprinkler v1.1 adds support for many stations/zones on: April 10, 2012, 11:53:20 am
Hi,

I am happy to announce a recent update to OpenSprinkler, which is an open-source, web-based sprinkler timer we've been working on since October last year. It is based on ATMEGA328 mcu, ENC28J60 Ethernet controller, and the Arduino software. The OpenSprinkler allows you to set water schedules and check station status using a web browser.

The latest hardware update provides an easy and cheap way to support pretty much any number of stations/zones you want. The software has also been updated to support a large number of stations. In addition, I've written an OpenSprinkler Arduino library, which you can use to create your own applications.

For details, please check out: http://rayshobby.net/?p=2339
Software and hardware design download: http://rayshobby.net/?page_id=202

Thanks!

Update release video:
12  Topics / E-Textiles and Craft / 'Sewing' electronics using wire wrap wires instead of conductive thread on: November 20, 2011, 11:35:07 pm
Not sure if anyone has tried this, but for a recent school project I experimented with using wire wrap wires (or any 30AWG or thinner wires) for 'sewing' electronic components to fabric or clothes. Well, it's not exactly sewing, because it's more like weaving wires through the fabric, and soldering components onto the wires. Also, it doesn't really involve a sewing needle because the wire itself is good enough to penetrate through fabric. I like the solderability, because I am really not good at sewing. Also, these wires are available in many stores and are cheap. I've documented the process (with pictures) in this blog article: http://rayshobby.net/blog/?p=1128. If anyone has tried this, please feel free to share your experience.
13  Using Arduino / Programming Questions / Re: A suggestion for the Arduino's shiftOut function on: October 24, 2011, 07:31:27 am
Great. Thanks, Bill and Rob.
14  Using Arduino / Programming Questions / A suggestion for the Arduino's shiftOut function on: October 24, 2011, 12:14:05 am
I encountered a minor issue with the Arduino's shiftOut function, which took me a while to find out. I thought I should share it in case other people encounter the same problem. The current implementation of this function is as follows:
Code:
void shiftOut(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, uint8_t val)
{
uint8_t i;

for (i = 0; i < 8; i++)  {
if (bitOrder == LSBFIRST)
digitalWrite(dataPin, !!(val & (1 << i)));
else
digitalWrite(dataPin, !!(val & (1 << (7 - i))));
digitalWrite(clockPin, HIGH);
digitalWrite(clockPin, LOW);
}
}

Note that this assumes the clockPin is LOW when this function is called, because the shift register will only accept value on the dataPin on a rising edge of the clockPin. The problem I encountered is that my clockPin is shared with the LCD. Sharing pins itself should not be an issue since both the shift register and the LCD have their own 'enable' pins, so they won't interfere with each other. However, with the current way the shiftOut function is implemented, upon calling this function, clockPin's status is unknown due to the pin sharing, thus it will cause problems with a missing rising edge.

My suggestion is to add digitalWrite(clockPin, LOW); right before the for loop, thus asserting clockPin to be LOW before entering the loop. Alternatively, move this line to right before the if statement as follows:

Code:
void shiftOut(uint8_t dataPin, uint8_t clockPin, uint8_t bitOrder, uint8_t val)
{
uint8_t i;

for (i = 0; i < 8; i++)  {
digitalWrite(clockPin, LOW);
if (bitOrder == LSBFIRST)
digitalWrite(dataPin, !!(val & (1 << i)));
else
digitalWrite(dataPin, !!(val & (1 << (7 - i))));
digitalWrite(clockPin, HIGH);
}
}

I think this is more robust anyways, since it's not a good idea to assume that clockPin is unaltered outside this function. Hope my suggestion makes sense.
15  Topics / Home Automation and Networked Objects / Re: Introducing OpenSprinkler: An Open-source Web-enabled Sprinkler Valve Controller on: October 14, 2011, 12:46:44 pm
Hi Rob,

I agree the timing is not the best. Well, I just happen to finish the project a week ago, so I thought it's better to post it than to wait. I can use the winter to improve the work smiley

Yes, there is a way to stop the valves manually, even when it's in 'web mode'. That's by pressing and holding the second button. Also, if you turn off the power switch, all valves will be closed (they can only be activated when power is on).

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