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buggstar
Joined: 28 Feb 2007
Posts: 3
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 28 Feb 2007 6:01 How to Setup 30pcs 12V bulbs? Circuit design help... |
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Hi Guys,
I need help to come up with a simple DC circuit:
1. Powered up by an AC Adapter
2. Connect 30pcs 12VDC bulbs
The 12VDC bulb is small (about 1cm length) I bought from a local electronics shop.
For reasons I can't explain, the bulbs have no polarity, but during the demo, it was powered up by a 9VDC battery!
I've searched around (for LED circuits) and found out that I can do it in a serial/parallel connection.
I'm not too sure on the resistors needed and the proper way to link them up in a circuit...
Thanks guys.
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Cortex
Joined: 26 Mar 2005
Posts: 179
Helped: 8
Location: Morocco
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| 28 Feb 2007 8:00 How to Setup 30pcs 12V bulbs? Circuit design help... |
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Hi
you can use a Small 12V transformer!
Or just resitors if nobody is going to touch the lamps(risky)!
the 12 bulbs can be connected in parallel ! but you can use a mix of parallel/serial connection
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buggstar
Joined: 28 Feb 2007
Posts: 3
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| 28 Feb 2007 8:59 Re: How to Setup 30pcs 12V bulbs? Circuit design help... |
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Hi Cortex, thanks for your reply and your help!
Silly me, I totally missed out the transformer!
But then, can the 240VAC supply be stepped down to 12VDC directly?
Attached here is a diagram I got from a website (but it is for LED circuit).
Mine are bulbs, not LED. But can this be used?
Please help, thanks in advance...
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Fragrance
Joined: 26 Jul 2002
Posts: 1326
Helped: 23
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| 28 Feb 2007 15:17 Re: How to Setup 30pcs 12V bulbs? Circuit design help... |
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| buggstar wrote: |
Hi Guys,
I need help to come up with a simple DC circuit:
1. Powered up by an AC Adapter
2. Connect 30pcs 12VDC bulbs
The 12VDC bulb is small (about 1cm length) I bought from a local electronics shop.
For reasons I can't explain, the bulbs have no polarity, but during the demo, it was powered up by a 9VDC battery!
I've searched around (for LED circuits) and found out that I can do it in a serial/parallel connection.
I'm not too sure on the resistors needed and the proper way to link them up in a circuit...
Thanks guys. |
led has ploarity as they are semiconductor device normal tungston buld has no polarity you can supply power in any directon, 30bulb you want to drive from 12 volt required parrallel connection and required lot of current the better solution is to drive them from main supply with out transformer and used serial connection what kind of main supply in your country 220v or 110v, and used heat srink cable to isolate the pin, to prevent electric shock
simply do this
for 110 and 220v volt
number bulbs x 12v= volt
regards
Fragance
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dkace
Joined: 13 Jun 2002
Posts: 356
Helped: 24
Location: Greece
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| 28 Feb 2007 15:33 Re: How to Setup 30pcs 12V bulbs? Circuit design help... |
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I don't agree either with the LED solution neither with the series solution. Things are quite simple:
Check the Wattage of the bulbs ( POWER disipation in each one of them). If it is say 10Watts each, then do as following:
SAY you have a 220V as main supply. Then Connecting all the bulbs in parallel will cost you : 30x10=300Watts. therefore 300W / 220V= 1.36Amps rouphly 2 Amps total current. You will use a 5Amp 220V fuse.
First thing is to fuse the circuit. Then, take a transformer 220V AC - 12V AC . Cost around 5Euro.
After the transformer connect a rectifier of 12V, 5Amp. Cost around 2 Euro. There you are! After the rectifier you may get a fluxuation of +/- 2V or 5V. If this is not adecuate ( bulbs are not designed for such fluxuation) then attach 2 zenner diodes with Vzenner=12V.
Now you can supply the whole 30 bulbs in parallel with this mini power supply.
I think this is the most efficient you can do. In order not to have a big thermo disipation on the rectifier, try to attach it to a cooling element ( aluminium plate or other).
Is the above near to want you want to do?
D.
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daviddlc
Joined: 11 Feb 2007
Posts: 99
Helped: 6
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| 01 Mar 2007 8:54 Re: How to Setup 30pcs 12V bulbs? Circuit design help... |
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Dkace your solution is the most expensive
And you need to do the current calculation with 12 volts instead 220 Volts.
So let's asume that bulb power is 1 watt, since 10 watts is to much
Then the right calculation for 30 bulbs 1 watts using 12 volts is like:
Watts = 30 bulbs x 1 watt = 30 Watts.
Current = 30 Watts / 12 Volts = 2.5 amps.
Then you need to buy or build a 220 VAC to 12 Volts 3 Amps power supply (which is cheaper than the 220VAC to 12 volts 5 amps). And if you want to use Zeners you need to consider the Zener current, if you use the wrong one, you can burn the Zener.
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The cheapest way is to connect the bulbs in serial/parallell circuit. But is more dangeorus if you don't know how to deal with high voltages
You can connect 15 bulbs in series and adding an extra resistance to a 220 volts power supply
The 15 bulbs in series will consume:
15 bulbs * 12 volts = 180 volts
Then the resistance needs to consume
220 volts - 180 volts = 40 volts.
To calculate the right resistance value you will need to know the current.
So if the bulb is 12 volts 1 watt, then the current is:
Current = 1 watt / 12 volts = 0.08333 Amps.
Then the resistance value should be:
Resistance = 40 volts / 0.08333 Amps = 480 ohms
You also need to calculate the power disipation for the resistance;
Watts = 40 volts * 0.083333 Amps = 3.3333 watts
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Remember that if you use a serial circuit and one bulb gets damaged, the other bulbs will not turn on.
While in a parallell circuit this is not a problem
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