Show Posts
Pages: 1 ... 36 37 [38] 39 40 ... 177
556  Using Arduino / LEDs and Multiplexing / Re: use 1 pin from arduino for bi color LED? on: January 10, 2014, 02:03:33 am
2 pins from your arduino instead?
557  Using Arduino / Project Guidance / Re: Controlling 1440W 120V coil resistor heater on popcorn popper with arduino uno on: January 10, 2014, 01:13:44 am
ohhh, sorry my mistake..

then cool, yeah you could use PWM on an SCR to control the current to the popcorn maker, an SCR sounds like a good way to go in which case.
558  Using Arduino / LEDs and Multiplexing / Re: Shift Register 74HC595 issue on: January 10, 2014, 12:21:14 am
Shiftout only sends 1bytes worth of data to the IC.

8bits worth, the next time you use shiftout, 8 more bits get shifted into the first register any bits previously store get shifted out to the 2nd register.

So the trick is to get the high/low values and send it in 2 lots (16bits)
559  Using Arduino / LEDs and Multiplexing / Re: use 1 pin from arduino for bi color LED? on: January 10, 2014, 12:14:44 am
What's the LED? if it's 3 pins no..
560  Using Arduino / Motors, Mechanics, and Power / Re: Maximum relays able to be controlled by Uno on: January 10, 2014, 12:09:57 am
A 7hc595 shift register will control 8 relays, 2 of them chained together  will give 16 outputs (or higher still with 3 or more)

Easy (3 pins to control hundreds of relays)
Forgive my ignorance.... but is the 7hc595 shift register already on the arduino board?

Uh, no.

If you wish to use just an Arduino, you'd have to turn ALL the pins into digital outputs including the analog ports, A0,A1.... etc which might supply enough pin outs.


http://www.ebay.com.au/itm/5-PCS-74HC595N-74HC-595N-595-8-bit-Shift-Register-IC-DIP-16-PIN-TEXAS-New-ICs-/270916565844?pt=AU_B_I_Electrical_Test_Equipment&hash=item3f13e2bb54


561  Using Arduino / Project Guidance / Re: Controlling 1440W 120V coil resistor heater on popcorn popper with arduino uno on: January 10, 2014, 12:07:16 am
A coil resistor?

I presume you mean Nichrome Wire (typically used in electric heaters) ... it comes in different flavors you also need to take into account it's AC and the impedance ... i'll be honest i'd stay well away from this.

but, the resistance is based on how much coil you use ....

So, once you've measured the length of wire, calculated it's resistance, housed it in a safe manner to not execute yourself,  all you'll need is a mechanical relay and a fuse (with a fuse inline with the nichrome wire) ...  I really don't recommend using a TRIAC or DIAC or SCR's because they're mainly used to control the current flow, where as a mechanical relay or SSR would just switch it on and over and does with... a TRIAC is a lot more complicated.

Further more, electric blankets rectify the AC voltage via a couple of diodes, again I'm not sure why as i STAY AWAY from 240v applications it's just not worth it when you can buy a popcorn maker and sleep safe knowing if something happens you can sue them  smiley-twist

 
562  Using Arduino / Project Guidance / Re: How to avoid arduino from starting over each time I unplug it. on: January 09, 2014, 11:59:35 pm
Quote
May i ask as to why you need to unplug it?...

I was wondering too... maybe it's in an exhibition hall and needs to be powered down for safety after hours or something? Maybe the cleaners need the power socket for the vacuum cleaner?

in which case,  it might be worth running it from a couple of batteries (which can be charged when it's plugged in, it's added complexity though)
563  Using Arduino / Project Guidance / Re: How to avoid arduino from starting over each time I unplug it. on: January 09, 2014, 11:47:41 pm
May i ask as to why you need to unplug it?...

A button to shut it down would be an idea, and then increment the eeprom a byte at a time to store the location until you hit the end and begin at the start, it would take many many years to wear out the eeprom like that (wiping the last value to 0 so you can search)

another option would be to save the location onto an SD card on an Ethernet shield and use a jump/goto to carry on where you left off.



564  Using Arduino / General Electronics / Re: ON/OFF circuit when it receive 3v signal. transistor? relay? on: January 09, 2014, 11:38:09 pm
0.6v is enough to make the transistor conduct.

you may need to place a diode or 2 to drop the voltage to near 0v   to prevent the transistor switching on with 1v.
.

565  Using Arduino / General Electronics / Re: ON/OFF circuit when it receive 3v signal. transistor? relay? on: January 09, 2014, 10:59:22 pm
is the signal digital? 3v on 0v off?

if so yes a transistor will do the job, you may have issues if it's a varied signal and you'd need a schmitt trigger to give a clean transition.
566  Using Arduino / General Electronics / Re: A capacitor is charged and discharged every 0.01 s on: January 09, 2014, 10:07:54 pm
Yes  smiley-confuse

Only did it the once though!  smiley-cry
567  Using Arduino / General Electronics / Re: A capacitor is charged and discharged every 0.01 s on: January 09, 2014, 07:56:32 pm
This site frequently use terms such as "explode" and "go on fire" or "burst into flames"

Having been professionally involved in the electronics game in one sense or the other for almost 60 years I have experienced capacitors "popping", "bursting" or "leaking";  resistors "smoking";   semiconductors "popping" and "smoking" and various components glowing rather well  --  but  NEVER "exploding", "going on fire" or "bursting into flames"

I fear there are too many out there who are either overly cautious or trying to scare the living daylights out of those who wish to learn.

So, FEAR NOT, exercise caution, destroy a few components, be prepared to turn off the power when the magic smoke starts to appear, but, most of all,  have FUN experimenting !!

That's true... but you know what you're doing, tell me what happens if you use a 5v rated cap in a 12v circuit like some here would and do....
568  Using Arduino / General Electronics / Re: Electronics current rating and Wire size question on: January 09, 2014, 07:52:58 pm
Hi! Im just wondering why a small Mosfet legs can handle 100A+ but wires needs to be very big to handle the same current?

Wires ard made up a finer twisted copper wire, the legs on a transistor are solid so there's more area for the electrons flow but even so a transistor can get very hot without heatsinking ....
569  Using Arduino / Motors, Mechanics, and Power / Re: Control 220v home appliances with Arduino. on: January 09, 2014, 07:48:34 pm
A safer option (if you still want to proceed).

Use an old power supply and remove the rectifier circuit so you end up with a low voltage AC, use the breadboard and learn to control low voltage AC... a small bulb rated for your supply will allow you to learn safely and when and only when it's working....

Build it, test with low voltage ac... if success wire up the 240v mains to it, hide it away in a non conductive case, stand well back, maybe a prayer (if religious) and throw the power switch lol
570  Using Arduino / Motors, Mechanics, and Power / Re: Maximum relays able to be controlled by Uno on: January 09, 2014, 07:40:45 pm
A 7hc595 shift register will control 8 relays, 2 of them chained together  will give 16 outputs (or higher still with 3 or more)

Easy (3 pins to control hundreds of relays)
Pages: 1 ... 36 37 [38] 39 40 ... 177