High power driver newbie question

Hi

You will have to excuse my newb questions, because I'm on a steep learning curve having programmed nothing since a Commodore PET and a BBC micro back in the 80's and once managed to make a flip-flop circuit at college!

But I have done a lot of reading and have a very basic knowledge of what I'm trying to achieve!

I've been playing with simple routines to get led's lighting and fading quite well (even managed to blow up a 14m2! )

What I'm trying to achieve is 6 led arrays (3 white in each) in sequence, fading in, one at a time, when triggerd by a sensor/switch, then holding on for a set time before sequentially fading off:

1 fade on
2 fade on
.
.
.
6 fade on
Hold for set time
1 fade off
2 fade off
.
.
.
Wait until next trigger

The sequence to be reversed when triggered from another sensor/input

I have managed to achieve this using switches and single white led's.

I now need to be able to drive the 6no. 3 led arrays. Problem is there is no spec on each array so I have no idea what the forward voltage or current is and whether the picaxe can drive the load without damage.

Can anyone help me out with this?

Thanks

I'd suspect the current would be a little too high for the PicAxe.

Try running the LED arrays from a 10V - 15V supply, with a 100 ohm series resistor and then checking the voltage across the LED array. If it is close to 8V, the LED array is presumed to be a series array (and requires more voltage than a PicAxe could happily provide), if closer to 3V, the LED array would be presumed to be a parallel array.

If you measure the volt drop across the 100 ohm resistor, the current drawn can be calculated by dividing the volt drop, by the resistance. If the volt drop across the resistor is 9V, the current draw would be 0.09A (9v/100 ohm=0.09A, or 90mA).
90mA would be more than a PicAxe would be happy with. 20-25mA per PicAxe pin is the usual limit.

That's quite a project when you have little experience and no information or specifications about the LED arrays.

Each array will need a PWM source and a driver. A Picaxe has a maximum of 4 PWM outputs. This could be done in a relatively straight forward manner using 2 Picaxe 14M2's and 6 NPN transistors. However, with no specs, the Voltage/Current to drive the LED arrays needs to be determined by testing as indicated above by tmfkam. This will determine what value current limit resistors will be needed and what supply voltage will be needed.

It could also probably be done with "multiplexing" but would be a quite a bit more complicated.

The term "high power" in regards to LED's is rather meaningless. "High Power" could mean anything from 30ma to 5 amps.

Can you describe the LED arrays? Are the LED's 3mm, 5mm, 7mm ? Are they in series or parallel?
Where did you get the LED arrays from? Can you at least provide a link to where they were purchased?

The more information you can provide the better quality help you will receive.

@Danno72 - welcome to this forum - sounds like what you are trying to do is quite possible - it would be good to have more information on what the loads are in terms of voltage and current - perhaps you should add an inexpensive multimeter to your repertoire! Then you could measure and tell us more what you need to do. The 14M2 is quite good with its 4 PWMOUTs - I've used it for light control.

PS Welcome back Goey... how's it going?

Thanks guys for the prompt replies

I am using these led's from a decking light kit, thats been kicking around in my shed for years.

http://www.ledgrouprobus.com/catalogue/l3/product?item_id=R3LED10-01

They are a 5mm cool white led arranged in threes. Thanks to the clear potting I can make out a smd resistor with 161 written on it. I think they would be parallel.

Since my 1st post, I have had an array running happily on 5v, but have yet to work out what the current draw is. From memory, measure in series? The only way I have to measure that is with my 240v rated meter as I'm an electrician. I only have a cheap multimeter which bought to practise with.

I am happy with just running 4 PWM channels for now, just so I can learn how to a) Write the program, and b) Remember how to construct a circuit! Its been 20 years!

I'll get to the 6 channels when I can get these arrays working properly. I don't want to end up drowning in information overload!

Where is the power supply that came with these lamps? If you can find it and measure the output voltage, you will be ahead of the game.

Thats the problem.

Just been looking for that. Unfortunately all I have is the lamps and nothing else. No instructions, no power supply, just the remains of the box!

I had a similar set of RGB a few years ago, that looked identical, but different manufacturer, they ran on 5v.

I finally managed to find the power supply. It is running at 5v output.

I've been looking at logic level mosfets and its all a bit over my head. All I need is a way of powering 3 white led's per output from the picaxe, and all I'm reading is gate capacitance and saturated this etc. I can see how to connect the mosfet, just unsure which one to use.

Can someone point me in the right direction?

Also I need a reliable way to trigger the lights to come on. I've been looking at small PIR modules or these:

http://www.electroschematics.com/wp-content/uploads/2010/03/HOA1405-Datasheet.pdf

Your advice would be greatly received.