| Author |
Message |
Electronic Swear
Guest
|
 Posted:
Fri Feb 04, 2005 7:09 am Post subject:
High AC voltage convert to DC voltage on driving IC |
|
|
Currently I am designing a circuit for controlling motor.
And I need to convert a 230Vac to 12Vdc for supply low voltage IC. In
the past, because of low power consumption for IC, I just use some
resistors and transistor for this convertion.
________ ___ C E
230Vac o-----| |---|_R_|--+----+------\ /-----o 12V
output
| diode | | | ---
| bridge | --- | ___ B
| | --- +-|_R_|--+
o-----|________| | |
GND |
12v Zener
|
|
GND
Now, I have changed some components and it need more current to drive
it. And the past design is not enough to do so. Now, I want to know
any similiar simply circuit can convert 230Vac to 12V dc with arround
200mA current.
If I replace the transistor to the TO-220 7812, can it supply enough
output for me to use? Thanks~
|
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Tim Hubberstey
Guest
|
| Posted:
Fri Feb 04, 2005 8:00 am Post subject:
Re: High AC voltage convert to DC voltage on driving IC |
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|
Electronic Swear wrote:
| Quote: | Currently I am designing a circuit for controlling motor.
And I need to convert a 230Vac to 12Vdc for supply low voltage IC. In
the past, because of low power consumption for IC, I just use some
resistors and transistor for this convertion.
________ ___ C E
230Vac o-----| |---|_R_|--+----+------\ /-----o 12V
output
| diode | | | ---
| bridge | --- | ___ B
| | --- +-|_R_|--+
o-----|________| | |
GND |
12v Zener
|
|
GND
Now, I have changed some components and it need more current to drive
it. And the past design is not enough to do so. Now, I want to know
any similiar simply circuit can convert 230Vac to 12V dc with arround
200mA current.
If I replace the transistor to the TO-220 7812, can it supply enough
output for me to use? Thanks~
|
First, please go find a sturdy wall and recite the following while
banging your head on the wall:
"It is a very, very, very, very bad idea for a hobbyist to use a
non-isolated power supply".
The point you have labelled as "GND" actually has about 110 VRMS on it
when plugged in. There is also no current limiting of any kind so it is
a lethal combination.
Go to your nearest electronics store and buy a "wall wort" (wall plug-in
supply) to use as a starting point. You can either get a DC output that
already has the diodes and filter inside (very easy to find) or, if you
want the design challenge, get an AC output unit and build your own.
Given your apparent level of experience, I suggest you get a DC wort.
To you get a regulated output from a 7812, you need at least 14 VDC on
the input when under load. The more input voltage you have available,
the hotter the 7812 will get. Try to get a 15 VDC wort but anything up
to 24 V should work, as long as you put a big enough heat sink on the
7812. With 24 V in and 200 mA out, the 7812 will be dumping 2.4 watts
and will require a decent heat sink. Google for "thermal resistance" if
you want to calculate what kind of heat sink you'll need.
--
Tim Hubberstey, P.Eng. . . . . . Hardware/Software Consulting Engineer
Marmot Engineering . . . . . . . VHDL, ASICs, FPGAs, embedded systems
Vancouver, BC, Canada . . . . . . . . . . . http://www.marmot-eng.com |
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Winfield Hill
Guest
|
| Posted:
Fri Feb 04, 2005 8:13 am Post subject:
Re: High AC voltage convert to DC voltage on driving IC |
|
|
Electronic Swear wrote...
| Quote: |
Currently I am designing a circuit for controlling motor.
And I need to convert a 230Vac to 12Vdc for supply low voltage IC.
In the past, because of low power consumption for IC, I just use
some resistors and transistor for this convertion.
________ ___ C E
230Vac o---| |---|_R_|--+----+------\ /-----o 12V
| diode | | | --- output
| bridge | --- | ___ B
| | --- +-|_R_|--+
o---|________| | |
GND |
12v Zener
|
GND
Now, I have changed some components and it need more current to drive
it. And the past design is not enough to do so. Now, I want to know
any similiar simply circuit can convert 230Vac to 12V dc with arround
200mA current.
If I replace the transistor to the TO-220 7812, can it supply enough
output for me to use? Thanks~
|
Awwkk!! Awwkk!! Troll alert! Troll alert!!!!
--
Thanks,
- Win
|
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| Back to top |
|
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Tim Hubberstey
Guest
|
| Posted:
Fri Feb 04, 2005 8:56 am Post subject:
Re: High AC voltage convert to DC voltage on driving IC |
|
|
Winfield Hill wrote:
| Quote: | Electronic Swear wrote...
[really bad idea snipped]
Awwkk!! Awwkk!! Troll alert! Troll alert!!!!
|
How can you tell? I can remember doing this kind of thing when I was too
young to know better so I know it could be real. I do _hate_ to waste
time on trolls, though.
--
Tim Hubberstey, P.Eng. . . . . . Hardware/Software Consulting Engineer
Marmot Engineering . . . . . . . VHDL, ASICs, FPGAs, embedded systems
Vancouver, BC, Canada . . . . . . . . . . . http://www.marmot-eng.com |
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|
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Electronic Swear
Guest
|
| Posted:
Fri Feb 04, 2005 1:24 pm Post subject:
Re: High AC voltage convert to DC voltage on driving IC |
|
|
Actually, I have changed to use 7812 on supply regulated voltage for
low voltage IC. The circuit is as following:
________ ___ ______
230Vac o-----| |---|_R_|--+-------+--| 7812 |-----o 12V
| diode | | + | --+--- | +
| bridge | --- | | ---
| | --- zener | ---
o-----|________|--+ | | | |
| GND GND GND GND
GND
Is it better to do so?
However, the R will be in very high WATT and what can I to do so?
Sorry, I am not familiar with such voltage convertion circuit. :(
Tim Hubberstey <bogus@bogusname.com> wrote in message news:<JGAMd.147$pN3.70@edtnps84>...
| Quote: | Electronic Swear wrote:
Currently I am designing a circuit for controlling motor.
And I need to convert a 230Vac to 12Vdc for supply low voltage IC. In
the past, because of low power consumption for IC, I just use some
resistors and transistor for this convertion.
________ ___ C E
230Vac o-----| |---|_R_|--+----+------\ /-----o 12V
output
| diode | | | ---
| bridge | --- | ___ B
| | --- +-|_R_|--+
o-----|________| | |
GND |
12v Zener
|
|
GND
Now, I have changed some components and it need more current to drive
it. And the past design is not enough to do so. Now, I want to know
any similiar simply circuit can convert 230Vac to 12V dc with arround
200mA current.
If I replace the transistor to the TO-220 7812, can it supply enough
output for me to use? Thanks~
First, please go find a sturdy wall and recite the following while
banging your head on the wall:
"It is a very, very, very, very bad idea for a hobbyist to use a
non-isolated power supply".
The point you have labelled as "GND" actually has about 110 VRMS on it
when plugged in. There is also no current limiting of any kind so it is
a lethal combination.
Go to your nearest electronics store and buy a "wall wort" (wall plug-in
supply) to use as a starting point. You can either get a DC output that
already has the diodes and filter inside (very easy to find) or, if you
want the design challenge, get an AC output unit and build your own.
Given your apparent level of experience, I suggest you get a DC wort.
To you get a regulated output from a 7812, you need at least 14 VDC on
the input when under load. The more input voltage you have available,
the hotter the 7812 will get. Try to get a 15 VDC wort but anything up
to 24 V should work, as long as you put a big enough heat sink on the
7812. With 24 V in and 200 mA out, the 7812 will be dumping 2.4 watts
and will require a decent heat sink. Google for "thermal resistance" if
you want to calculate what kind of heat sink you'll need. |
|
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|
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James Meyer
Guest
|
| Posted:
Fri Feb 04, 2005 6:29 pm Post subject:
Re: High AC voltage convert to DC voltage on driving IC |
|
|
On 3 Feb 2005 23:24:25 -0800, swear_terence@hotmail.com (Electronic Swear)
wroth:
| Quote: | Actually, I have changed to use 7812 on supply regulated voltage for
low voltage IC. The circuit is as following:
________ ___ ______
230Vac o-----| |---|_R_|--+-------+--| 7812 |-----o 12V
| diode | | + | --+--- | +
| bridge | --- | | ---
| | --- zener | ---
o-----|________|--+ | | | |
| GND GND GND GND
GND
Is it better to do so?
However, the R will be in very high WATT and what can I to do so?
Sorry, I am not familiar with such voltage convertion circuit. :(
|
___ ________ ___ ______
230Vac o--- |_C_|--| |---|_R_|--+-------+---| 7812 |-----o 12V
| diode | | + | --+--- | +
| bridge | --- | | ---
| | --- zener | ---
o-----|________|--+ | | | |
| GND GND GND GND
GND
Add a capacitor between the 230Vac and the diode bridge. That will drop
the voltage without getting hot. Use a non-polarized (not electrolytic)
capacitor. The voltage rating should be 400 volts and the value probably needs
to be at least 1 microfarad. The R value can then be reduced so that it doesn't
get too hot.
Jim |
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Mook Johnson
Guest
|
| Posted:
Fri Feb 04, 2005 7:05 pm Post subject:
Re: High AC voltage convert to DC voltage on driving IC |
|
|
I agree with the previous poster. It is very dangerous to use power from
the lines this way. You cold kill youself or so unsuspecting person that
happens across your device.
I would HIGHLY recommend using the Wall arts idea followed by a regultor or
puttin a dedicated transformer between the 230VAC and your curcuit. A fuse
would also be highly recommended so you don't burn the place down if things
go wrong.
In the current design below you will most certainly blow the 7812. When
there is no load on the output, the input will likely rise above its input
voltage rating and kill the device.
If you need help sizing a transformer or wallwart for the application, thet
good folks here would be glad to help of you give voltage output current
requirements for the power supply.
"Electronic Swear" <swear_terence@hotmail.com> wrote in message
news:910532f6.0502032324.9411d5f@posting.google.com...
| Quote: | Actually, I have changed to use 7812 on supply regulated voltage for
low voltage IC. The circuit is as following:
________ ___ ______
230Vac o-----| |---|_R_|--+-------+--| 7812 |-----o 12V
| diode | | + | --+--- | +
| bridge | --- | | ---
| | --- zener | ---
o-----|________|--+ | | | |
| GND GND GND GND
GND
Is it better to do so?
However, the R will be in very high WATT and what can I to do so?
Sorry, I am not familiar with such voltage convertion circuit. :(
Tim Hubberstey <bogus@bogusname.com> wrote in message
news:<JGAMd.147$pN3.70@edtnps84>...
Electronic Swear wrote:
Currently I am designing a circuit for controlling motor.
And I need to convert a 230Vac to 12Vdc for supply low voltage IC. In
the past, because of low power consumption for IC, I just use some
resistors and transistor for this convertion.
________ ___ C E
230Vac o-----| |---|_R_|--+----+------\ /-----o 12V
output
| diode | | | ---
| bridge | --- | ___ B
| | --- +-|_R_|--+
o-----|________| | |
GND |
12v Zener
|
|
GND
Now, I have changed some components and it need more current to drive
it. And the past design is not enough to do so. Now, I want to know
any similiar simply circuit can convert 230Vac to 12V dc with arround
200mA current.
If I replace the transistor to the TO-220 7812, can it supply enough
output for me to use? Thanks~
First, please go find a sturdy wall and recite the following while
banging your head on the wall:
"It is a very, very, very, very bad idea for a hobbyist to use a
non-isolated power supply".
The point you have labelled as "GND" actually has about 110 VRMS on it
when plugged in. There is also no current limiting of any kind so it is
a lethal combination.
Go to your nearest electronics store and buy a "wall wort" (wall plug-in
supply) to use as a starting point. You can either get a DC output that
already has the diodes and filter inside (very easy to find) or, if you
want the design challenge, get an AC output unit and build your own.
Given your apparent level of experience, I suggest you get a DC wort.
To you get a regulated output from a 7812, you need at least 14 VDC on
the input when under load. The more input voltage you have available,
the hotter the 7812 will get. Try to get a 15 VDC wort but anything up
to 24 V should work, as long as you put a big enough heat sink on the
7812. With 24 V in and 200 mA out, the 7812 will be dumping 2.4 watts
and will require a decent heat sink. Google for "thermal resistance" if
you want to calculate what kind of heat sink you'll need. |
|
|
| Back to top |
|
|
lemonjuice
Guest
|
| Posted:
Fri Feb 04, 2005 10:05 pm Post subject:
Re: High AC voltage convert to DC voltage on driving IC |
|
|
On 3 Feb 2005 17:09:34 -0800, swear_terence@hotmail.com (Electronic
Swear) wrote:
| Quote: | Currently I am designing a circuit for controlling motor.
And I need to convert a 230Vac to 12Vdc for supply low voltage IC. In
the past, because of low power consumption for IC, I just use some
resistors and transistor for this convertion.
________ ___ C E
230Vac o-----| |---|_R_|--+----+------\ /-----o 12V
output
| diode | | | ---
| bridge | --- | ___ B
| | --- +-|_R_|--+
o-----|________| | |
GND |
12v Zener
|
|
GND
Now, I have changed some components and it need more current to drive
it. And the past design is not enough to do so. Now, I want to know
any similiar simply circuit can convert 230Vac to 12V dc with arround
200mA current.
If I replace the transistor to the TO-220 7812, can it supply enough
output for me to use? Thanks~
|
Some ideas ...
Unless you're interested in investigating your sensory and muscular
response to electrical stimulus you need to put an optoisolator at the
output and better still connect it to a triac or a relay... make sure
the closing time of your relay is less then that of your heart beat to
avoid premature death. Place a resistor and a fuse there too.
Further precautions would be ...
At the 240V output I'd place a fuse 100mA or whatever you need as
current and a fusible resistance 200ohms.
Other ideas ... to avoid heat dissipation is to use a capacitor of the
suppressor type then a resistor before the diode bridge as power
dissipated by a capacitor is less then a resistor of the same
impedance voltage and current being out of phase.
I'd connect a capacitor then a regulator or some zeners to get a low ac
voltage in that point go for something like a total of 16volts .
maybe this is clearer
fuse fuse resistor
live o-o_/ \o--|___|-------|
.-.
resistor | |
1k | |
'-'
|+
Capacitor == +230v input /-\ \. to diode
|------------- bridge
| /´
V
z zener
|
|
z
A zener
neutral---------------------|
Well the part after the diode bridge is simpler... add another
capacitor above 40uF then in parallel a Resistor plus a 12 V zener
across which you'll have your load connection. do your calculations
.... I = E/ 1/2*pi* 50(or60) *C .
IMO you can do without the transistor. If you need current above 50mA
.... your capacitors become very big and so expensive. Not much point
then of doing without a transformer.
BTW
Disclaimer: The author assumes no liability for any incidental,
consequential or other liability from the use of this information. All
risks and damages, incidental or otherwise, arising from the use or
misuse of the information contained herein are entirely the
responsibility of the user. |
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Rob Gaddi
Guest
|
| Posted:
Sat Feb 05, 2005 12:11 am Post subject:
Re: High AC voltage convert to DC voltage on driving IC |
|
|
Hear hear. You specced 12V, 200mA. I'd overrate the wart to 300mA just
to give yourself some room to play. 12V DC, 3.6W adapter. If that
costs you $10 you overpaid for it. Doing your own off-line regulation
when you have pretty trivial power requirements doesn't start to pay
until you're cranking them out by the thousand.
Mook Johnson wrote:
| Quote: | I agree with the previous poster. It is very dangerous to use power from
the lines this way. You cold kill youself or so unsuspecting person that
happens across your device.
I would HIGHLY recommend using the Wall arts idea followed by a regultor or
puttin a dedicated transformer between the 230VAC and your curcuit. A fuse
would also be highly recommended so you don't burn the place down if things
go wrong. |
|
|
| Back to top |
|
|
Rich Grise
Guest
|
| Posted:
Sat Feb 05, 2005 12:40 am Post subject:
Re: High AC voltage convert to DC voltage on driving IC |
|
|
On Thu, 03 Feb 2005 23:24:25 -0800, Electronic Swear wrote:
| Quote: | Actually, I have changed to use 7812 on supply regulated voltage for
low voltage IC. The circuit is as following:
________ ___ ______
230Vac o-----| |---|_R_|--+-------+--| 7812 |-----o 12V
| diode | | + | --+--- | +
| bridge | --- | | ---
| | --- zener | ---
o-----|________|--+ | | | |
| GND GND GND GND
GND
Is it better to do so?
|
No. You are still going to kill yourself or worse, somebody else.
| Quote: | However, the R will be in very high WATT and what can I to do so?
Sorry, I am not familiar with such voltage convertion circuit. :(
|
Here's a place to start:
http://www.bestbuy.com/site/olspage.jsp?j=1&&CategoryID=cat08103&id=1051384550149&skuId=3857017&type=product&ref=21&loc=01
check out these links:
http://www.google.com/search?q=dc+wall+adapter
Good Luck!
Rich |
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Jamie
Guest
|
| Posted:
Sat Feb 05, 2005 1:07 am Post subject:
Re: High AC voltage convert to DC voltage on driving IC |
|
|
Electronic Swear wrote:
| Quote: | Currently I am designing a circuit for controlling motor.
And I need to convert a 230Vac to 12Vdc for supply low voltage IC. In
the past, because of low power consumption for IC, I just use some
resistors and transistor for this convertion.
________ ___ C E
230Vac o-----| |---|_R_|--+----+------\ /-----o 12V
output
| diode | | | ---
| bridge | --- | ___ B
| | --- +-|_R_|--+
o-----|________| | |
GND |
12v Zener
|
|
GND
Now, I have changed some components and it need more current to drive
it. And the past design is not enough to do so. Now, I want to know
any similiar simply circuit can convert 230Vac to 12V dc with arround
200mA current.
If I replace the transistor to the TO-220 7812, can it supply enough
output for me to use? Thanks~
yes, the 7812 is fine for your needs how ever, your input voltage must |
be dropped down using a transformer which is much safer in the long run.
get a transformer that will give you a drop to around 16.. 24 Vac. then
pass that to a bridge rectifier, Cap and then 7812.
the 7812 is rated for 1 amp and needs a heat sink., in your case of
200 mA, keeping the input voltage 3 volts (after filtering) above as a
min should produce a smooth stable regulation for the 7812. if you keep
the input voltage not much above the output voltage , the 7812
will be in near saturation state and thus can be operated with out the
heat sink at 200 mA . the lower resistance effects will produce much
less heat. |
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