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1  Using Arduino / Installation & Troubleshooting / Re: [SOLVED] Deek/Dswy Robot Mini Pro - can't upload a sketch & bootloader on: April 03, 2014, 01:29:28 pm
Hi,
thanks so much for posting the solution!! A life saver!
I bought 5 of these Arduinos, already installed some of them in my project and then wasn't able to upload any sketches. The Nano as ISP method worked perfectly! smiley-wink All 5 Minis saved!

Chris
2  Using Arduino / General Electronics / Re: does a "normally closed" transistor or similar exist? on: October 23, 2013, 12:00:38 pm
The Arduino built-in PWM is around 800Hz. So that would require external PWM components, which would cancel out the advantages of the solid state relay.
Thanks for the suggestion though... smiley-wink
3  Using Arduino / General Electronics / Re: does a "normally closed" transistor or similar exist? on: October 23, 2013, 11:52:29 am
I've not really looked at these solid state relays in detail but at first glance they don't seem to be fast enough for PWM dimming.
4  Using Arduino / General Electronics / Re: does a "normally closed" transistor or similar exist? on: October 23, 2013, 11:50:34 am
So would this work?
5  Using Arduino / General Electronics / Re: does a "normally closed" transistor or similar exist? on: October 23, 2013, 11:36:28 am
Thanks for all the replies.
I think for now it's good to know that depletion mode MOSFETs exists, but if the same can be done with a "normal" MOSFET and a few components, then I'll go for that as I already have some normal MOSFETs that I can use.

I'll update my circuit diagram to add the small transistor on the gate of the MOSFET and change some resistor values (according to Pelleplutt's post) and will post it again.
6  Using Arduino / General Electronics / Re: does a "normally closed" transistor or similar exist? on: October 22, 2013, 06:27:04 pm
Thanks for that. I was unaware of these.
But hmmm... They need a negative voltage. I would have to generate that just for the MOSFET.

I've come up with the attached circuit in the meantime. Looks like that might work.

This is going to be for a home automation project. I want to be able to control a lamp (LED) from both a wall switch and an Arduino. The wall switch must always work as if it was a normal switch (for the wife smiley-wink )
7  Using Arduino / General Electronics / Re: does a "normally closed" transistor or similar exist? on: October 22, 2013, 01:49:15 pm
Actually, a pull-up on the Base using the LED voltage would be enough, wouldn't it. Then switch the Base LOW to switch off the LEDs.

I had a feeling that would be a silly question.... smiley-wink
8  Using Arduino / General Electronics / does a "normally closed" transistor or similar exist? on: October 22, 2013, 01:39:09 pm
Hi,

I want to control and dim (PWM) LED light strips with an Arduino. However, I want the LEDs to also work (full brightness) in case the Arduino goes down for some reason.
I've done PWM dimming on LEDs before with the Arduino but there the switching transistor / MOSFET would of course be off if it gets no power or no signal from the Arduino.

So I'm looking for something that behaves like a transistor but basically opens when want to but is closed without input.
9  Using Arduino / Networking, Protocols, and Devices / Re: RF1100-232 serial to RF transceiver module on: September 02, 2013, 01:41:25 pm
I just remembered, you need to leave a 1-2 second pause before each command otherwise the module will send it as a data stream. And you need to send the commands in binary, not as text or so.
10  Using Arduino / Networking, Protocols, and Devices / Re: RF1100-232 serial to RF transceiver module on: September 02, 2013, 11:46:18 am
Hi,
the config commands for the module are on my website (but I think you may have them already)
http://www.yesyes.info/index.php/electronics/rf1100-232-rf-433mhz-transceiver-module/

You can either connect the module to a TTL level USB to serial adapter, connect that to a computer and then run my configurator program (also on that website) to configure it. Then disconnect the module and connect it to the Arduino. That's how I do it currently. The module remembers its settings without power. However, don't hardwire the module. Occasionally it seems to forget a setting and you will need to disconnect it from the Arduino and configure it again.

The other alternative is to include the module configuration into your Arduino sketch in the setup() function. (this function is being executed once when the Arduino starts up). The tricky part is to configure the baud rate of the module this way. You will need to send the command with the baud rate that the module is currently configured to. In many cases this is not known. So you will need to open and close the Arduino serial port with different baud rates and send the "set baud rate" command. Luckily the module only supports 3 baud rates (4800, 9600 and 19200), so you will only need to do this twice (you don't need to do it with the baud rate you want, because that would be set already). Then, once you have set the baud rate, you open the Arduino serial port with that baud rate and send the remaining commands. I'm planning to do that in my sketches but have not got around to it yet.

I hope that makes any sense. If not, please do ask... ;-)
11  Using Arduino / Sensors / Re: sensing mains power on: July 24, 2012, 03:46:58 am
Thanks a lot for all the replies...
I think the neon lamp + LDR is the most sensible and easiest option. I'll go for that. It will be a while yet before I get around to actually implementing that. I'll report back if there are any issues.

Thanks again for all the suggestions! smiley
12  Using Arduino / Sensors / Re: sensing mains power on: July 20, 2012, 03:31:42 am
That's the kind of idea I was hoping for.. ;-)

So with the neon and LDR solution, all I need on the mains side is one of these:
http://cgi.ebay.co.uk/ws/eBayISAPI.dll?ViewItem&item=120842237010&fromMakeTrack=true&ssPageName=VIP:watchlink:top:en
and a 470k resistor?
On the Arduino side just an LDR pulling an input low, or even using an analogue input and another resistor forming a voltage divider with the LDR.

You mention a cap, where would that go in this case?
Would a normal 1/4W resistor be enough for the neon? Or does this need to be one with a higher wattage rating?
13  Using Arduino / Sensors / Re: sensing mains power on: July 19, 2012, 08:20:26 am
Quote
A capacitor over led/optocoupler is no problem.
Except for the voltage rating it has to be.

The "flashing LED" circuit on the web page I linked to uses a 47uF 10V capacitor. Do you think the capacitor should be rated as high as the "mains dropper" capacitor?
14  Using Arduino / Sensors / Re: sensing mains power on: July 19, 2012, 08:16:17 am
you can use an AC 230V (or 110V) microrelay to send a DC signal to your arduino. Simple!

Not a bad idea. But I can't find one that is smaller than the LED circuit....
15  Using Arduino / Sensors / Re: sensing mains power on: July 19, 2012, 08:15:12 am
Quote
Does this look OK?
Looks fine, appart from the fact I would also have a resistor in line with the LED. The only thing limiting the current is te 470R and the 0.15uF cap, I am not sure if that will pass too much current.

How would you calculate the value for that resistor?
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