Low current efficient 4.5v reg. wanted.

R

Russell Griffiths

Guest
Greetings.
I have a project in mind based around a cordless doorbell.
The receiver is powered from 4.5v.

I would like to use a 12v 1.2Ah rechargeable battery to power
the receiver, and need a 4.5v regulator that uses very very
little current itself.

I will need to use the 12v supply to power another part of the project.

Is there a low current reg. like a 78L05 that is more efficient and
can be set at 4.5v.

Thanks.
Russell.
 
rg26ce1991@hotmail.com (Russell Griffiths) wrote in
news:13cdb672.0410270541.2d0c3a72@posting.google.com:

Greetings.
I have a project in mind based around a cordless doorbell.
The receiver is powered from 4.5v.

I would like to use a 12v 1.2Ah rechargeable battery to power
the receiver, and need a 4.5v regulator that uses very very
little current itself.

I will need to use the 12v supply to power another part of the project.

Is there a low current reg. like a 78L05 that is more efficient and
can be set at 4.5v.

Thanks.
Russell.
Click to expand...


For more efficiency than a linear you have no choice but to go switch-mode.
The National semi "simple switcher" series is easy to use and has low parts
count. You can probably expect about 85% efficiency, depending on load
though.

It would be more beneficial by far to put the design effort into reducing
the current requirements of your receiver than the power supply. This is
where you can make great gains. My Arlec cordless cheapie doorball receiver
lasts months on 2 AA cells.
 
On 27 Oct 2004 06:41:41 -0700, rg26ce1991@hotmail.com (Russell
Griffiths) wrote:

Greetings.
I have a project in mind based around a cordless doorbell.
The receiver is powered from 4.5v.

I would like to use a 12v 1.2Ah rechargeable battery to power
the receiver, and need a 4.5v regulator that uses very very
little current itself.

I will need to use the 12v supply to power another part of the project.

Is there a low current reg. like a 78L05 that is more efficient and
can be set at 4.5v.

Thanks.
Russell.
Click to expand...

Hello Russell,
just for fun I had a look at the 78L05 data sheet.
http://www.onsemi.com/pub/Collateral/MC78L00A-D.PDF
on page 2
input bias current typical 3.8 mA and max 6 mA
I am assuming that is the current consumed while the
device is not supplying the load and you want better
than that. Wow!

Again just for fun I opened up a mobile phone charger,
the type that plugs into a cigarette lighter in a car.
Inside is this IC
http://www.onsemi.com/pub/Collateral/MC34063A-D.PDF
The bottom of page 3 says Total device 4 mA

I measured 13 mA input current to the charger on a 12 V
supply but it had a LED indicator as well. The LED is
probably using most of the input current.

The reason I took an interest in this, was, that you
can buy these cigarette lighter chargers, cheaply, from
Oatley Electronics. I received one of their e-mails yesterday.
http://www.oatleyelectronics.com/2dollarshop.html
http://www.oatleyelectronics.com/pdf/gcl3.pdf

The car charger that I opened up came from Dick Smith,
sold on special as a phone accessory in a box with leather
case and earplugs for varous phones. These accessory boxes
ranged in price from $10 to $1 to even eleven cents.
The MC34063 IC itself costs around $5 dollars

What I am leading up to tell you is, try one of these el-cheapo
swich mode power supplies (which you will have modified to
give your desired output voltage according to the instructions
on the Oatley link) and see what the overall efficiency is with
your particular load at 4.5 or 5 volts.

Compare the efficiency of the 78L05 regulator using the
same load.

Russell, I am a cheapskate when it comes to my
electronics hobby but I don't think you can beat that.
Oh! wait a sec! I spoke to soon. You could put a
self tapping screw into the lead link that connects
the cells together on your battery.
That would give you roughly 4 and a bit Volts.
Might be enough.
You didn't say what the current consumption
of the receiver is. If it is small, maybe just tapping
the battery will be fine.

Regards,
John Crighton
Hornsby
 
"John Crighton" <john_c@tpg.com.au> wrote in message
news:418045b6.19581718@News.individual.net...
On 27 Oct 2004 06:41:41 -0700, rg26ce1991@hotmail.com (Russell
Griffiths) wrote:

Greetings.
I have a project in mind based around a cordless doorbell.
The receiver is powered from 4.5v.

I would like to use a 12v 1.2Ah rechargeable battery to power
the receiver, and need a 4.5v regulator that uses very very
little current itself.

I will need to use the 12v supply to power another part of the project.

Is there a low current reg. like a 78L05 that is more efficient and
can be set at 4.5v.

Thanks.
Russell.


Hello Russell,
just for fun I had a look at the 78L05 data sheet.
http://www.onsemi.com/pub/Collateral/MC78L00A-D.PDF
on page 2
input bias current typical 3.8 mA and max 6 mA
I am assuming that is the current consumed while the
device is not supplying the load and you want better
than that. Wow!

Again just for fun I opened up a mobile phone charger,
the type that plugs into a cigarette lighter in a car.
Inside is this IC
http://www.onsemi.com/pub/Collateral/MC34063A-D.PDF
The bottom of page 3 says Total device 4 mA

I measured 13 mA input current to the charger on a 12 V
supply but it had a LED indicator as well. The LED is
probably using most of the input current.

The reason I took an interest in this, was, that you
can buy these cigarette lighter chargers, cheaply, from
Oatley Electronics. I received one of their e-mails yesterday.
http://www.oatleyelectronics.com/2dollarshop.html
http://www.oatleyelectronics.com/pdf/gcl3.pdf

The car charger that I opened up came from Dick Smith,
sold on special as a phone accessory in a box with leather
case and earplugs for varous phones. These accessory boxes
ranged in price from $10 to $1 to even eleven cents.
The MC34063 IC itself costs around $5 dollars

What I am leading up to tell you is, try one of these el-cheapo
swich mode power supplies (which you will have modified to
give your desired output voltage according to the instructions
on the Oatley link) and see what the overall efficiency is with
your particular load at 4.5 or 5 volts.

Compare the efficiency of the 78L05 regulator using the
same load.

Russell, I am a cheapskate when it comes to my
electronics hobby but I don't think you can beat that.
Oh! wait a sec! I spoke to soon. You could put a
self tapping screw into the lead link that connects
the cells together on your battery.
That would give you roughly 4 and a bit Volts.
Might be enough.
You didn't say what the current consumption
of the receiver is. If it is small, maybe just tapping
the battery will be fine.

Regards,
John Crighton
Hornsby
Click to expand...
Let us know the max current consumption you need. That would help a lot. I'd
say a 78L05 would be fine for your application with a drop down diode to
around 4.6V.
-Phil
 
"Phil" <reply to thread> wrote in message news:<4180556c$0$21703$afc38c87@news.optusnet.com.au>...
"John Crighton" <john_c@tpg.com.au> wrote in message
news:418045b6.19581718@News.individual.net...
On 27 Oct 2004 06:41:41 -0700, rg26ce1991@hotmail.com (Russell
Griffiths) wrote:

Greetings.
I have a project in mind based around a cordless doorbell.
The receiver is powered from 4.5v.

I would like to use a 12v 1.2Ah rechargeable battery to power
the receiver, and need a 4.5v regulator that uses very very
little current itself.

I will need to use the 12v supply to power another part of the project.

Is there a low current reg. like a 78L05 that is more efficient and
can be set at 4.5v.

Thanks.
Russell.


Hello Russell,
just for fun I had a look at the 78L05 data sheet.
http://www.onsemi.com/pub/Collateral/MC78L00A-D.PDF
on page 2
input bias current typical 3.8 mA and max 6 mA
I am assuming that is the current consumed while the
device is not supplying the load and you want better
than that. Wow!

Again just for fun I opened up a mobile phone charger,
the type that plugs into a cigarette lighter in a car.
Inside is this IC
http://www.onsemi.com/pub/Collateral/MC34063A-D.PDF
The bottom of page 3 says Total device 4 mA

I measured 13 mA input current to the charger on a 12 V
supply but it had a LED indicator as well. The LED is
probably using most of the input current.

The reason I took an interest in this, was, that you
can buy these cigarette lighter chargers, cheaply, from
Oatley Electronics. I received one of their e-mails yesterday.
http://www.oatleyelectronics.com/2dollarshop.html
http://www.oatleyelectronics.com/pdf/gcl3.pdf

The car charger that I opened up came from Dick Smith,
sold on special as a phone accessory in a box with leather
case and earplugs for varous phones. These accessory boxes
ranged in price from $10 to $1 to even eleven cents.
The MC34063 IC itself costs around $5 dollars

What I am leading up to tell you is, try one of these el-cheapo
swich mode power supplies (which you will have modified to
give your desired output voltage according to the instructions
on the Oatley link) and see what the overall efficiency is with
your particular load at 4.5 or 5 volts.

Compare the efficiency of the 78L05 regulator using the
same load.

Russell, I am a cheapskate when it comes to my
electronics hobby but I don't think you can beat that.
Oh! wait a sec! I spoke to soon. You could put a
self tapping screw into the lead link that connects
the cells together on your battery.
That would give you roughly 4 and a bit Volts.
Might be enough.
You didn't say what the current consumption
of the receiver is. If it is small, maybe just tapping
the battery will be fine.

Regards,
John Crighton
Hornsby


Let us know the max current consumption you need. That would help a lot. I'd
say a 78L05 would be fine for your application with a drop down diode to
around 4.6V.
-Phil
Click to expand...
Greetings from Russell.
Thanks for doing the experiment and research John.
The current draw of the doorbell at 4.5v is 0.4mA. The doorbell instructions
claim a life of around 6 months.

I know from a previous project that a 7905 reg. uses 1.2mA.

The idea of the car charger is interesting, but I am wondering if
a switching regulator would interfere with the receiver in the doorbell.

Thankyou to all who posted.

The 78L05 probably will be fine, but I just wondered what other ideas
the group might have to keep the current low.
If I use at least a 1.2Ah battery, it should last long enough in between
charges.

But I may end up using a 9v battery. I need 9-12 v to power other
parts of the project.

Thakyou,
Russell Griffiths.
 
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