132 replies to this topic

[Maxlaam]

Make it a series and use the pre-made examples as a guide, those would be beginner and intermediate. You can probably make the advanced yourself. Just make a new thread for it and post examples in single osts with a tag saying Easy, Hard, Advanced or something. If you are unhappy about the lay-out contact me and I will re-arrange them, however I can not change the order of posts.

[floris2burn]

I just noticed I forgot to put a diode over the relay in part 3.3.2.

[floris2burn]

Ok, after adding the whole thing about drawing SFC's yesterday, I now added the part about actually coding the darned thing.

I'm also wondering if it'd be useful if the GKD would be translated to dutch?

[TheSUCKCrew]

Okay, I have a good tip to you all:
Re-using old electronics is a very good idea to save money (like: Using old cables that you found in your garage, or taking components from an old PC) but be sure to test them out before actually using them.
For example, I've had to redo my whole control-panel for Power Tower 2 because it seemed like I had some unwanted connection on my perfboard.
So I redid the whole thing, and ran a few tests again, and had exactly the same problem.
What happened: I used an old Sub-D cabel to connect the panel to my arduino, but that cable was messed up. There were a lot of connections within that thing.

[LaMbChOpZ]

Just a question, if wiring LEDs together, what would be a good amount of LEDs to group together in a series? I was thinking maybe 4 or 5.

[Maxlaam]

You can't just say "I'll wire 4 or 5 in series", you have to calculate the amount of possible leds in series and that does include a resistor.

I can't help you if you give me no information at all. Power-supply voltage, current, how much current and voltage does a LED require?

[TheSUCKCrew]

^^ Well, assuming that you are gonna use my lightsign driver, you will have 0,5amp per output. An LED uses approx 20mA, so 500 / 20 gives you 25 leds per parallel group. My driver allows an input of 12 volts and an LED takes a maximum of 3 volts, so that would be 12 / 3 = 4 parallel groups in series per output.

Edit: Oops, I didn't really read your question correctly. Max, you don't need to know the current if you are grouping things parallel. You will only need voltage. The power can be up to 12 volts, so that would be 12 / 3 = 4 leds in series. So you will definitly need to put some leds parallel.

[Maxlaam]

^ Well, assuming that you are gonna use my lightsign driver, you will have 0,5amp per output. An LED uses approx 20mA, so 500 / 20 gives you 25 leds per parallel group. My driver allows an input of 12 volts and an LED takes a maximum of 3 volts, so that would be 12 / 3 = 4 parallel groups in series per output.

You can't just assume that stuff. It's not some kind of guessing unless you want to either burn through your LEDs or ruin your power-supply. You need to know what he's going to work with.

Furthermore, I run my red/green/yellow (aka the standard colours) at 1.9V, bright enough. Most of them are rated at 2.1V though. 3V may seem a bit too much for the regular colours. Most noticeable with green/yellow LED's. The colours go odd when you put too high of a voltage on them. I always, ALWAYS check the datasheet of something I'm going to work with.

Edit: How can you say you don't need to know the current? You can't just keep running lights in parallel.

[TheSUCKCrew]

You can't just assume that stuff. It's not some kind of guessing unless you want to either burn through your LEDs or ruin your power-supply. You need to know what he's going to work with.

Furthermore, I run my red/green/yellow (aka the standard colours) at 1.9V, bright enough. Most of them are rated at 2.1V though. 3V may seem a bit too much for the regular colours. Most noticeable with green/yellow LED's. The colours go odd when you put too high of a voltage on them. I always, ALWAYS check the datasheet of something I'm going to work with.

Edit: How can you say you don't need to know the current? You can't just keep running lights in parallel.

I can assume he will use my driver because he asked me to make him one. Leds are generally very alike, so I can assume they will take approx 3 volts and 20mA. Yes, a bit more information about what LEDs he is going to work with wouldn't hurth indeed, but other than that we can pretty accurately calculate everything already.

You only need to know the current when you are working with parallel, and he is asking about serial.

[Maxlaam]

I can assume he will use my driver because he asked me to make him one. Leds are generally very alike, so I can assume they will take approx 3 volts and 20mA. Yes, a bit more information about what LEDs he is going to work with wouldn't hurth indeed, but other than that we can pretty accurately calculate everything already.

You only need to know the current when you are working with parallel, and he is asking about serial.

I'm not talking about your driver in my post, I'm talking in general. You can't assume, you need to calculate. Always.

I'm pretty sure you don't want him to come back to you a day after receiving your driver telling you it doesn't work because he shorted/burned it out. LEDs can take a bit of a beating but still, electronics are delicate pieces. Especially PIC's, which are on your light sequencer. Just some static current from your clothing can burn it through.

Yes he asked for series, and in that case you are right, you don't need to know the current to determine the amount of LEDs in series, still current is not something you can neglect at any point.

[LaMbChOpZ]

How about we start with the LED's themselves, then work out the series or parallel deal?


Power Supply
- AC Power Supply
- 120 V (60 Hz if this helps)



These LED's will be used in individual letters, not mixed (one letter is entirely blue, next is entirely yellow).

Yellow
- 2.4V Forward (3V Maximum)
- 3V Continuous Forward Current


Blue
- 3.5V Forward (4V Maximum)
- 30V Continuous Forward Current

[Maxlaam]

You are missing something. I highly doubt you are going to use a 120V power supply (that's the American wall-socket rating right?). That's probably the power-supply input voltage. What comes out? What kind of voltage, how much current can it handle? It should be listed on a label somewhere.

I'd like to see a datasheet from your LEDs. You are giving numbers that I can not relate to.

Also we NEED to know the current your LEDs draw so you can calculate the maximum parallel series.

[floris2burn]

A quick guide to figure some things out on driving leds:

Get the proper datasheets for the components you're going to use.
Remember, voltage is in volts, current in amps.

Now, you'll probably start off with a certain power supply you can find. This PSU will have a certain voltage and the maximum current it can give on that voltage. (DC power supply is needed for driving leds)

Then, to get the amount of leds you can put in series, get their forward voltage. This depends on the color etc. This is mostly somewhere between 1-2 Volts. Divide the PSU's voltage by the led's voltage, then round this number down. If it's too close, substract another. For example: 5.05 possible leds, make it 4.
That is because you need to calculate the required resistor to limit the current. This shouldn't be the maximum allowed current for the LEDs, you can do fine on 10-20% of that current.

After that, you duplicate this series diagram into a parallel branches. This will increase the current you draw. At some point, you'll start drawing too much current from either the PSU or whatever system you use to switch the LED's on or off.

I hope this clarifies things.

[TheSUCKCrew]

^^^^ You say that one can't assume and that I need to calculate, but I can also calculate based on my assumptions, and give him an approximate number of leds.

Especially PICs? That is not true at all. Any microchip is very sensitive, also the ones that you find on professional lightsequencers.

Current is deffinatly something you can neglect at some points. That is whenever it doesn't matter in your calculations.

[LaMbChOpZ]

I'm actually starting to lean to using 9V battery(s). I'm not guaranteed the availability to have an outlet, so I may want to look into battery-operated logo.

Blue LED

Yellow LED.


Right now, I'm still trying to figure out just how many LED's I'll be using, but I'm approximating that there will be between 15 to 30 LED's per letter. That's what I need to figure out tonight.

[floris2burn]

Seems like the yellow works on 2.4-3 Volts, and the blue one on 3.5-4 Volts.

On a 9V battery, you can put 2 LED's in series, that isn't much. But it's also pretty high for an LED, did i get the wrong values?
Maybe try different colors?

[TheSUCKCrew]

^^ I wouldn't try batteries.

Watch out Max, assumptions are coming:

Spoiler

Assuming that you will be using 6 letters with 25 leds each, that all draw 3 volts and 25mA, you will be able to split them up in series of 3, so that would be 150 / 3 = 50 parallel groups, 50 * 25mA = 2,5amps. A good 9 volts battery gives you 1200mAh, which means you will be able to run the sign like half an hour per battery. This is just an estimation, it can be even worse! So I wouldn't recommend that.

[LaMbChOpZ]

^^ Problem is, it's school colors, the name is the school mascot, and the track color is school colors as well, it'll be a little hard to change it.


^ So would going to an outlet work better then?

[Maxlaam]

^^^^ You say that one can't assume and that I need to calculate, but I can also calculate based on my assumptions, and give him an approximate number of leds.

And that is where it goes wrong already in this case, he's using a specialty colour like blue which has very different ratings that the standard leds. He still needs to calculate it himself. For his leds.

Especially PICs? That is not true at all. Any microchip is very sensitive, also the ones that you find on professional lightsequencers.

Seriously... Things like this are pissing me off a lot.

Current is deffinatly something you can neglect at some points. That is whenever it doesn't matter in your calculations.

At some points, but I wouldn't call it neglect. More like "You don't need it for this calculation."

[floris2burn]

Try using the PSU of an old computer, those things can give a lot of Amps for a small (or no) price.