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166  Using Arduino / Project Guidance / Re: board with GPS on: August 02, 2014, 09:47:27 pm
Your cat will  hide where there's no signal smiley
167  Using Arduino / General Electronics / Re: How to filter power supply for NeoPixel circuit on: August 02, 2014, 09:40:24 pm
 What's the power source?

A couple of large caps to deal with the power supply, then feed that to the 7805?

Hard to imagine without a circuit
168  Using Arduino / General Electronics / Re: Cheap Soldering Iron Problems on: August 02, 2014, 09:04:40 pm
If my soldering station fails how do I repair it   smiley-eek
169  Using Arduino / Programming Questions / Re: Need some quick help with flashing leds on: August 02, 2014, 09:16:36 am
... and just what is the purpose of digitalRead from a pin that's state is an output?  Won't it just toggle?
170  Using Arduino / Project Guidance / Re: Super Simple Sine Wave genorator on: August 02, 2014, 09:03:04 am
I actually built the sine wave circuit and then fed it an underpowered 3watt led..


But even so after probing it with a cheap oscilloscope, the sinewave from a 555 looks like a sinewave over a triangle or square wave...


The cal slowly charges and discharges, the opamp detects 1/3 the voltage but it's slowly charging a cap, how's this modified sinewave take place?
171  Using Arduino / Project Guidance / Re: Super Simple Sine Wave genorator on: August 02, 2014, 04:25:08 am
If it's purely a sinewave,  do you require it drop below 0v  eg  5v to -5v or just 0v to 5v?


172  Using Arduino / General Electronics / Re: Question regarding transistors. on: August 02, 2014, 01:24:40 am
You really need to get a better understanding / an understanding. .. of ohms law, then you need to understand the basics of a transistor esp it's gain.

Let's say you feed 1ma (an arduino supplies around 20ma comfortably) let's say the gain is 100  of the transistor this value varies sometimes 60 gain sometimes 200, darlington can be 2000 and higher, opamps higher still.


1ma to the base of transistor will amplify 100 times (transistor specific, datasheet) allowing around 100ma to flow between collector .
and emitter.

Since you can safely suck up 20ma from 1 arduino pin, you could supply 1ma to 20 resistors


Ohms law/transistor gain.
173  Using Arduino / General Electronics / Re: The terms "common emitter" and "emitter follower" on: August 02, 2014, 12:49:18 am
On an npn, it's about limiting the current from the arduino pin...

Via a resistor to base, and you'd be fine ... but under emitter follower,  swap the base transistor out and move it betwewn ground and the emitter..

Now even though there's no base transistor it's safe in the emitter follower example
174  Community / Bar Sport / Re: Overly expensive or ok? on: August 01, 2014, 09:36:34 pm
After thinking about it..... it has to be a rip off.
175  Community / Bar Sport / Overly expensive or ok? on: August 01, 2014, 09:33:45 pm
http://www.ebay.com.au/itm/ARDUINO-UNO-ENET-SCUOLA-LAB-KIT-Part-ARDUINO-K000005-/351041644928


Someone selling a starter kit for schools, just trying to work out if the price seems fair /or/ not.
176  Using Arduino / General Electronics / Re: Capacitor transistor problem on: August 01, 2014, 08:18:58 pm
Hi, I think Thereminx is doing it this way to understand the electronic circuitry rather than the programming.

Good first attempt, and MarkT's circuit will do what ThereminX is trying out.

Tom....... smiley


His circuit  should work with the correct resistor values, my concern with mark's is the way the pnp's pulled to ground.
177  Using Arduino / General Electronics / Re: Waveform Generation on: August 01, 2014, 12:02:14 pm
Everything you needed to know about the intersil wave gen..

I noticed the circuit is more cut down.
178  Using Arduino / General Electronics / Re: Capacitor transistor problem on: August 01, 2014, 11:54:25 am
I thought I'd give my own circuit a shot....


Increase the cap size for a longer fade/glow
179  Using Arduino / General Electronics / Re: Charging 2.7v supercap with 5v but monitor with analogRead() on: August 01, 2014, 11:07:23 am
It wouldn't stay at 2.7v long...
180  Using Arduino / General Electronics / Re: Charging 2.7v supercap with 5v but monitor with analogRead() on: August 01, 2014, 07:31:43 am
Might be worth investing some time on using 2 caps independent of each other but to use a switching method to use both caps in a charge pump circuit , the efficiency is the only concern
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