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376  Using Arduino / Project Guidance / Re: Turning off a high voltage circuit with D3, HIGH on: May 07, 2014, 09:23:38 pm
I'm using a medical device drill. Used in surgery.
Is this a high speed medical drill? Cutting the power to one of those won't stop it immediately, as there will be some run-on, dependent on friction. Also, if this is to be used in a medical situation, it wouldn't be a good idea to use a carbon brush for contact, as bits of carbon could break off and get into the patient, and a carbon brush probably wouldn't withstand sterilisation.
The manufacturer has told me is 15v DC and I'm waiting to see if they'll answer my questions regarding current. If they don't tell me, I guess I might have to break it to get a multimeter in there.
Then how do you propose to turn it on and off? As long as you can get to the 15V leads you can measure the current with a meter.
377  Using Arduino / Project Guidance / Re: Can the Arduino do this - power source switch on: May 06, 2014, 11:57:31 pm
What I'm suggesting is a rechargeable 6V battery that's charged overnight by the transformer. The battery can run the pump during the day when the solar cells are not giving sufficient power and be (slightly) recharged by them when they are getting a lot of sunlight. You don't need an Arduino for that.

Plug a time switch into your power socket and plug the transformer into that. Use the 6V to operate a relay. When the power is on (overnight) the relay pulls in and charges the battery through a diode. In the morning, the time switch shuts off the power to the transformer, the relay drops out and the battery is connected to the pump and solar cells.

I use a similar system for my emergency lighting, using a 12V car battery and a charger. Any time the mains fails, the charger stops holding the relay in and the emergency lights come on 'automagically'.  Beats having to find a torch in the dark when the RCD trips for no apparent reason.
378  Using Arduino / Project Guidance / Re: Cat chips. on: May 06, 2014, 11:21:06 pm
There was another Thread recently in which someone wanted to identify wagons on a model railway.
That was me. I've not done anything about it yet.
I was intrigued by the subject of this thread, as I initially thought it referred to some exotic foreign food substance.   smiley
Someone suggested using animal RFID tags and an RFID reader. That leads me to think you could read the cat chips with a separate reader connected to the Arduino. However I have never experimented with RFID.
Neither have I, but I'm assured it does work. What I couldn't find out was (for my own use, whether the pet tags could be reprogrammed, and) what is the frequency the pet tags work at. There are 3 types of RFID devices, standard, VHF and UHF. As the tags are very small, about the size of a grain of rice, I suspect they use UHF.
379  Using Arduino / Project Guidance / Re: Turning off a high voltage circuit with D3, HIGH on: May 06, 2014, 10:36:13 pm
I'm not clear what you want, but think of it as switching ON when the pin goes LOW.  You will need a transistor to switch the motor on and off, but we can't tell you which one until you tell us
1) the voltage ("I think it's 12V" isn't precise enough!), and
2) the current drawn by the motor.
Both of these should be marked on the drill.
380  Using Arduino / Project Guidance / Re: Breathing LED, PWM - Change duration of breath on: May 06, 2014, 09:48:46 pm
How long does the original code take to run 1 cycle? Looks about 10 seconds to me, but you have it set-up and can time it.
Divide 120 (= 2 minutes) by the number of seconds it takes, then multiply ALL the delays by the result (whole numbers only).  That should give you a cycle of ~2 minutes.
381  Using Arduino / Programming Questions / Re: Interruptions problem on: May 05, 2014, 11:53:41 pm
However, the main question is, why are you using interrupts in the first place ?
His motorbike is fitted with flux capacitors   smiley-grin smiley-grin smiley-grin smiley-grin
382  Using Arduino / Project Guidance / Re: Anyone have a 3d printer? on: May 05, 2014, 11:28:23 pm
Is there a maker group near you (you don't say where you are)? If there is, I'm sure you could get one of them to print your prototype for you (for the cost of the materials and a few pints of beer/bottles of wine).  smiley-cool
Much cheaper than buying your own 3D printer for a one off!  smiley-money
383  Using Arduino / Project Guidance / Re: please help, PIR sensor code problem on: May 05, 2014, 11:03:38 pm
You've set up an array called sequence but haven't used it anywhere.
I think that array should be an array of ints, not chars, as binaries are just numbers. You could write them as 1,3,7,15,31,63,127 and 255. The result will be the same.
384  Using Arduino / Project Guidance / Re: Can the Arduino do this - power source switch on: May 05, 2014, 10:31:50 pm
Is the pump always on (assuming full power from the solar cells) during daylight hours?
If not, have you thought about a storage device (rechargeable battery) to be charged when the pump is not on?
You could then recharge the battery overnight from the transformer.
All you'd need is a mains time switch to turn the transformer on and off (at dusk and dawn), a relay to disconnect the pump while the battery is being charged from the mains and a diode to stop the battery from holding the relay in when the transformer switches off.
385  Using Arduino / General Electronics / Re: Power supply from ATX PSU on: May 03, 2014, 09:46:31 pm
The switch should be momentary (a push to make button is usually used here), not the toggle switch you've shown. With a toggle switch you're turning the unit on and almost immediately back off again. On your computer you push once to turn it on and a second time to turn it off. The toggle switch is doing both actions, so you're not getting any power output.
386  Using Arduino / Programming Questions / Re: Interrupt function help on: May 03, 2014, 09:16:07 pm
No it won't. It may not be circular, but it has the same diameter all the way round (27mm*), as does the 20p coin (21.5mm*). It will always be the same height, whichever way up it is.
I never new that!
Each 'side' is an arc centred on the opposite point so that it will roll. The centre of rotation when rolling is not fixed, unlike a circular coin. Clever British design!
387  Using Arduino / Project Guidance / Re: Need Guidance on: May 03, 2014, 08:32:26 pm
First off, I have absolutely no clue what I am doing. All I know is how to solder, that electronics need a power supply and that usually wires need to be connected.

Now, what I want to do  is to transmit a wireless signal from one car to another, namely that a blinker has been activated, so that it would be able to warn a car 2 or even 3 cars back.

Thanks so much!
Please ask questions because I'm sure you need more info than that and also please help because I'm excited about this.
Nice safety idea but....
What you want can probably only be done with radio.
Radio transmitters are difficult to make directional, so the signal would propagate in all directions and be picked up by every car nearby, even those going in the opposite direction. Not too bad on a fairly quiet stretch of road, but imagine the effect in the midst of a traffic jam in a two-way street with everyone wanting to turn one way or another. I'd turn the damn thing off before attempting to drive in London.
And how many drivers don't bother to use their indicators when turning? In one place I know, it's as high as 80%.
388  Using Arduino / Programming Questions / Re: Interrupt function help on: May 03, 2014, 12:17:39 pm
Now try sorting out the problem of the 50p which is not round and the give different readings.
No it won't. It may not be circular, but it has the same diameter all the way round (27mm*), as does the 20p coin (21.5mm*). It will always be the same height, whichever way up it is.

*measured with a ruler, so not highly accurate.
389  Community / Bar Sport / Re: Stanford bioengineers create circuit board modeled on the human brain on: May 02, 2014, 11:28:46 pm
Whether or not I'd want one depends on who's brain it's modeled on.   smiley-wink
390  Community / Bar Sport / Re: Insane prices for Arduino clones on: May 02, 2014, 11:10:52 pm
My genuine Uno is a SMD model. It was bought for me as a present, so I can't complain! I got a Uno clone from China, yesterday, to play about with the chip (If I let out the smoke, at the price I paid, it's no great hardship!) and, as has been said, it worked straight from the box. I powered it up and the pin 13 LED was flashing at 1Hz. I suspect they loaded the flash sketch to test it. I loaded my own sketch and it worked perfectly...EXCEPT... the pin 13 LED is now on all the time! I've yet to try digitalWrite(pin13, LOW); to see if that cures it. But even if it doesn't, it's not a difficult job to remove the LED, if necessary.
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