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811  Community / Bar Sport / Re: Why don't CPUs and microcontrollers operate on 24v? on: October 11, 2012, 09:37:52 am
All the above, plus 24V lets the "magic smoke" outy-cool smile

But its a more impressive firework show than at 3v3  :-)
812  Community / Bar Sport / Re: I'm not a troll but.... on: October 11, 2012, 09:30:04 am
It was a Hydroponic controller it had to control water, temp, PH, nutrients, Lights ect.
All at the same time ie. multitask (something arduino cant do)

This all sounds rather slower than reflexes required for landing a Mars probe :-)

Surely the plants can wait a couple of loops through the program to get their water or nutrients ?
813  Using Arduino / Project Guidance / Re: inverting a VirtualWire (rx) signal on: October 11, 2012, 03:19:12 am
Looking again at the VW manual, the 2000 bit rate is used in his calculation, but later on he shows results at various speeds

At 7000bps, Range about 90m
At 5000bps, Range about 100m
At 2000bps, Range over 150m
At 1000bps, Range over 150m

I had switched to testing with softeasytransfer, ( which also has waveforem issues to cater for ) but might go back to VW at 5000 again to see what happens.
814  Using Arduino / Project Guidance / Re: inverting a VirtualWire (rx) signal on: October 10, 2012, 09:12:00 am
I had it running slower to start with but didnt like the look of the data ( but that was of course when I had the data inverted ) so without checking the VW recommendations, I just kept increasing the speed until it looked similar to the bursts from my TV remote ( I was thinking about the IR Rx bandwidth rather than the VW )

I am now going to play with the speed and see whats best.  Thanks for pointing that out .
815  Using Arduino / Project Guidance / Re: inverting a VirtualWire (rx) signal on: October 10, 2012, 08:59:42 am
@ Paul,  yes the data is inverted by IR receiver modules, the output is pulled up to 5v via a 10k, and bursts of of IR pull it down.

@ Crossroads, yes perhaps one transistor and a resistor is a lot easier than messing with the library  " when ignorance is bliss,  tis folly to be wise "

I am goig to play with the VW baud rate now, its running at 6000 at the moment, and the IR receiver module has a nice shaped waveform coming out.
816  Using Arduino / Project Guidance / inverting a VirtualWire (rx) signal on: October 10, 2012, 07:58:48 am

I am playing around using VirtualWire  on an infrared link, using a 38Khz receiver module.
I reckoned that as it has agc and data slicing like a rf module, the manchester encoding of VW should work well, and it does, but the receiver module has an inverted data output, so I have stuck a transistor inverter between it and the VW rx pin of the arduino.

Is there a way I can simply invert the signal from the VWrx  ?    ( there is an inverting option of the push to talk, but I need the data inverted )
817  Community / Bar Sport / Re: Let's do a rally of meaningless complaints on: October 10, 2012, 12:38:57 am
  " I hate those 3 day cruises they advertise,  a three day cruise is just a ferry with no GPS ! "   --  Joan Rivers
818  Using Arduino / Project Guidance / Re: What is the best way for controlling array of 8-16 relays? on: October 08, 2012, 10:39:50 am
1. If relays are powered from external power supply, should the grounds be connected?

definately, thats the common reference for both the logic and the driver parts of the chip.

2. Where to put capacitor and why it is needed?

You will always need a 100nF capacitor near to any chip, between the 5v and ground for decoupling,  and you will also need a 1000 MFd electrolytic close to the relays 12v supply, to smooth any surges as the relays open and close .

3. May I use arbitrary pins for data/latch/clock?

If you are using shiftout to switch the relays then you can choose the pins.  (  shiftout is easily fast enough for switching relays )

4. What will be the state of output pins on power on/restart?

You can  set up the state of the all the  pins during start- up.  (  or there is a simple way to store the states in eeprom at power-down, to reload at power up again )

819  Using Arduino / Programming Questions / Re: Multi drop com port on: October 08, 2012, 05:25:46 am
You could use SIM20 transceivers " One network could have maximum 255 nodes. " and I am getting 500 meters range with them ...
820  Using Arduino / Project Guidance / Re: What is the best way for controlling array of 8-16 relays? on: October 06, 2012, 04:53:00 pm
The circuit I showed will handle those relays easily, the chip is a lot faster than the relays.

I use the Shiftout function to drive the outputs ( I have strips of LEDs, but it could be relays)

The serial data through the first chip ( which is a shift register ) pin 18, feeds the serial in to the next pin3 input, and so on.

You can have as many chips as you like.
821  Using Arduino / Project Guidance / Re: What is the best way for controlling array of 8-16 relays? on: October 06, 2012, 12:23:30 pm
You can easily control 16 relays ( or as many as you like ) directly with 2 TPIC6B595 serial latches, with  3 wires to the Arduino chip. it only needs  2 components - plus a 100nF capacitor on each chips +5v pin of course  ( the chips have inductive protection diodes built in ) :-

822  Using Arduino / Project Guidance / Re: Infrared experiment- wheres this code from? on: October 06, 2012, 12:19:06 pm
Right, I tried running the above code as a seperate 38Khz generator, with the idea of feeding it to a transisitor, and externally gating the VirtualWire data with a diode.

As soon as I set the VW, however ,  the 38Khz dies,  so I am going to use a separate 555 timer to generate the 38Khz ( cutting edge eh? ) for the experiment, and come back later to the internal gating.
823  Using Arduino / Project Guidance / Infrared experiment- wheres this code from? on: October 06, 2012, 03:17:24 am

I am musing for the next project , about using  infrared to replace the wireless modules that I normally use .

I use either VirtualWire with the simplex modules, and lately SerialEasyTransfer with SIM20 modules.

I want to experiment with using an IR link having the VirtualWire ( or SET ) data  gating 38Khz bursts of data and the receiver using a normal  IR detect module, straight into the Rx ( or possibly inverted )   I can play with the baudrate to match the receivers bandwidth.

The VW library uses a preamble and manchester code, which might work well with the IR receiver.

All the IR projects I can find on the forum/playground are using one of the TV remote codes, which I am not interested in.

I want to knock up a quick experiment between 2 arduinos, and found the following code on Sparkfun for generating the 38Khz pulses, turned on and off at 500ms intervals

void setup() {               
  // toggle pin 11 on compare
  TCCR2A = _BV(WGM21) | _BV(COM2A0);
  TCCR2B = _BV(CS20);
  // 38kHz timer
  pinMode(11, OUTPUT);
void loop() {
  //turn the 38kHz carrier wave off and on           
  TCCR2B = 0;
  TCCR2B = _BV(CS20);
It works fine, the 38Khz is accurate, but the output when it toggles off can be left either high or low, which would be bad for driving ( via a transisitor )  an IR LED at high power, as it would burn out if the gaps were high -  I could use a cap in the driver, but I am sure there must be a way of holdng pin11 low.  TCCR2B = 0 perhaps ?or might that also leave the output high?

The trouble is I have no idea where this code comes from, there are no libraries called, and I did a search in the Arduino22 folder, but nothing.

I want to be able to gate this with the VW data ( even if I loop the VW Tx pin back into an input pin for the mock up experiment)

Perhaps I can digitalWrite pin 11 low when I want no output, or would it upset the toggling ?

824  Community / Bar Sport / Re: A project to prevent a homocide on: October 04, 2012, 05:51:16 pm

Yep, the old welding-slag-down-the-boots trick. Know it well, and they reckon I can't dance smiley


Just trying to picture a walkabout nomad in boots ( and a solar powered welder )  :-)
825  Community / Bar Sport / Re: A project to prevent a homocide on: October 04, 2012, 05:41:59 pm
Don't laugh, once I managed to step on a hot soldering iron while in sock feet.

On a serious note, I stepped on a burning charcoal from the barbeque 25 year ago, and just dunked my foot briefly in the swimming pool.
A friend told me to leave my foot in the pool for several minutes ( to stop it cooking ) but I knew better, and didnt even cover the blister when it burst.

I now have one foot 1 size bigger than the other while rested, and much bigger than that after standing or walking all day.
Luckily the climate here allows me to be barefoot, or to wear adjustable strap sandals all year, otherwise I would have a massive shoe budget !

OK, the producers of " Finding Bigfoot" can rest now, he is in Cape Town :-)

Oh dear, I have just noticed this is post 666 and I am a God member ?  :-(
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