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 powering via ac adapter
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By: Anonymous: bobdood () on Wednesday, December 12 2007 @ 04:19 PM PST (Read 7790 times)  
Anonymous: bobdood

The most practical means of powering these other than with a battery
would be to use a wall wart followed by a switch and a little conditioning
circuit consisiting of a voltage regulator, two capacitors, and an inductor.
I might make that an option later.



Let's say I need to complicate the kit as I need to plug it in and not use batteries! I'm a beginner so I'm interested in learning and using the kit for a project but absolutely need to avoid batteries, for installation reasons. Questions...!

If I find an appropriate ac adapter, can I just use that and safely wire it up directly to the kit (in place of the included battery pack wires)? This is preferred, even if the adapters costs a few bucks. Do the components inside ac adapters regulate the voltage safely enough for this idea to work long term with a kit like this that doesn't have resistors for the leds?

If that is not a doable way to go, and I have to plug directly into a wall socket (no transformer), then can you describe the components required for this more in depth? Wall wart, switch, regulator, inductor, 2 capacitors, like you say. What sizes and design do you recommend and where to purchase? Or is that just too much information and difficulty to give to a beginner?

Thanks, would like to buy a few of these kits if I can plug them in and have continuous operation while plugged in (no on/off switching required). This site rocks by the way...





       
   
By: Windell (offline) on Wednesday, December 12 2007 @ 05:20 PM PST  
Windell

No problem.

The project uses two AA cells in series, anything else that produces 3 V DC, +/- 10% at 50 mA or greater is suitable. Just wire it up where the battery wires went.

You should easily be able to find a suitable AC adapter; just make sure that it says "regulated" on it. Many adapters made for cell phones would work fine. If you find one that produces something more than 3 V and you want to use it (a 4.5 V supply, e.g.,) put a resistor in series with the input to drop some of the voltage.

>This site rocks by the way...

Thanks! Mr. Green


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By: Anonymous: bobdood () on Thursday, December 13 2007 @ 01:20 PM PST  
Anonymous: bobdood

put a resistor in series with the input to drop some of the voltage



I think I'd go for the robustness of having an adapter as well as these resistors, since many adapters are cheap and don't regulate properly and I want the device to work for as many years as possible. Newbie question... can you point me to any info on the web about this 'resistor in series' component/concept? Is that one resistor or many or just a purchasable component? And finally where do you mean 'with the input'? I assume you mean power input? Thanks so much for the help, just trying to figure out a little more about what type of resistor(s) to buy for this kit, even if using a 3V adapter as you suggest. Almost all the beginner/intermediate elec kits and led boards I see on the net involve batteries! As you say, I can see that it simplifies the design but me no likey likey.

That clay triangular fractal project kind of blew me away.





       
   
By: Windell (offline) on Friday, December 14 2007 @ 03:34 AM PST  
Windell

>Newbie question... can you point me to any info on the web about this 'resistor in series' component/concept? Is that one resistor or many or just a purchasable component?

Just one resistor. The battery box has two wires that go to the chip. Call the black one "ground," and the other is at 3V. Now, you cut the wires to the battery box and want to put a higher voltage source there. To bring it back to 3 V on the input, you hook up a resistor to the red wire coming off of the chip, and hook the other end of that resistor to your power supply. Use ohm's law (V = I*R) to figure out how much voltage is dropped across the resistor; err on the high side. Also note: you can only be a little bit above 3 V before the resistor dissipates too much heat; the power dissipated across the resistor is P=I*V, and for "usual" resistors, that's 0.25 W, max.


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By: Anonymous: bobdood () on Friday, December 14 2007 @ 09:05 AM PST  
Anonymous: bobdood

You rock for helping me. I am going to snatch up a few of your kits, and make these pieces as discussed. Now I feel more evil, and much better, thanks. Looking forward to messing around with the the chip programming, that is an area I'm much more comfortable with!





       
   
By: Anonymous: bobdood () on Thursday, January 03 2008 @ 12:35 PM PST  
Anonymous: bobdood

One last noob curiosity. May be totally out of scope for this forum, in that case perhaps you can point me somewhere on the web.

So what if I wanted to power up 2 or 3 or n kits at once with one adapter? Each 'kit' being 1 chip connected to 1 led display, everything just like your design defines, other than the AA pack. You've already helped me figure out how to power up 1 kit with 1 wall wart. Is there a component you can recommend buying which easily allows me to hook up a wall wart and then amplify/divide into the proper volts/amps required for each kit all powered up at once (3V and 50 mA each I believe)? If the divided power isn't exact then I can use resistors too... This all probably sounds hackish!





       
   
By: Windell (offline) on Thursday, January 03 2008 @ 12:44 PM PST  
Windell

Any number of kits can be powered from the same power supply. If you have ten kits that each run on 3 V and draw 50 mA, you can hook each of them across the 3 V from the power supply. Since those are being powered in parallel, each one draws 50 mA from the power supply, so the power supply would need to be capable of 500 mA.


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By: Anonymous: bobdood () on Thursday, January 03 2008 @ 02:20 PM PST  
Anonymous: bobdood

I see said the blind man. Thanks Evil Windell! You make it sound so easy. Just to confirm before I try some whack shit and blow up $100 worth of components, let me clarify the parallel hookups.

1. Does it mean the DC pos branches out to each kit, and the gnd from each kit all converge back into 1 branched connection back to the DC gnd? That doesn't seem right, but maybe it is.

2. Or do you mean, the DC pos connects to kit1, kit1 pos connects over also to kit2 pos, and so on back with kit 2 gnd connects to kit1 gnd connects to DC gnd. One big loop such that the DC wires each only have 1 other wire attached. That doesn't seem right either.

3. Or?





       
   
By: Windell (offline) on Thursday, January 03 2008 @ 02:40 PM PST  
Windell

I'm not certain what you mean by "pos"-- I'm guessing that you mean the "positive" power supply lead to each kit. Your description is not very clear to me, but I *think* that the two cases that you are describing are identical electrically, both examples of parallel circuits:
http://www.allaboutcircuits.com/vol_1/chpt_5/1.html
(imagine a whole kit where each resistor is.)

Let's go back to the case of just ONE kit running. Before you hook it up, your power supply (e.g., battery) has 3 V across the terminals but is producing no current. After you hook the kit up, positive terminal to positive terminal, negative terminal to negative terminal, the power supply *STILL* produces 3 V, but now is supplying up to 50 mA.

Now, ignoring the kit that's already hooked up, it's STILL a power supply with 3 V across the terminals, so you can hook another kit up to it. That kind of connection, multiple "loads" connected across the same power supply is called a parallel connection.

At some point if you put too many loads on it, the power supply current capacity may be exceeded. Say, it's rated for 500 mA and you tried to draw 600 mA from it. When that happens, the power supply will no longer put out 3 V, but some lower voltage, at which point all of the things hooked to that power supply are affected.


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By: Anonymous: bobdood () on Thursday, January 03 2008 @ 02:54 PM PST  
Anonymous: bobdood

Thanks, I'm sure I did a bad job of trying to explain the circuit examples. I think Option 1 is the parallel, thanks for the link, I see now that I need to do the pos and gnd branching for parallel power. I suppose I would just buy a little thruhole board and solder the power wires and connections there, unless there is a more obvious method you can point me to. I will send photos when done!





       
   
By: Anonymous: bobdood () on Thursday, January 03 2008 @ 03:18 PM PST  
Anonymous: bobdood

Thanks to your link, I have determined the terminal strip I think is the way for me to do the power hookups, this is the information I was looking for, I must thank you again.
http://www.allaboutcircuits.com/vol_1/chpt_5/8.html
As a noob trying to hack through this stuff your site and kits and forum and such have been invaluable. I will support y'all however I can in the future, in addition to buying goodies. Hail Ming, you have destroyed earth.





       
   



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