Reducing voltage from 12V to 9V on power supply

Frequently asked questions regarding powering your pedal.

Reducing voltage from 12V to 9V on power supply

Postby Super Locrian » 18 Sep 2013, 14:20

Hi all,

I have a T-Rex Fuel Tank Classic power supply that delivers 3 x 500 mA from three sections, 9V DC, 12V DC and 12V AC. I have exhausted the capacity of the 9V outlets (I only buy 9V pedals as a matter of principle), and so I wonder if there is a simple voltage reducing circuit that I can either put inside, or piggy-back on top of the Fuel Tank. I imagine T-Rex would just ignore me if I sent such a request to their customer support (or at best they would recommend purchasing another T-Rex product). My electronics knowledge is not exactly impressive, but I figure it should be a fairly simple deal to reduce the voltage. Is it just a matter or adding a resistor or two? I just need a simple schematic and parts list. Can anyone help? PS. I know a lot of 9V pedals can handle 12V too, but I don't want to risk anything, so I'd prefer to get the voltage down.
Super Locrian
 
Posts: 18
Joined: 18 Jul 2009, 15:29
Has thanked: 1 time
Have thanks: 0 time

Re: Reducing voltage from 12V to 9V on power supply

Postby alexradium » 18 Sep 2013, 14:42

Super Locrian wrote:Hi all,

I have a T-Rex Fuel Tank Classic power supply that delivers 3 x 500 mA from three sections, 9V DC, 12V DC and 12V AC. I have exhausted the capacity of the 9V outlets (I only buy 9V pedals as a matter of principle), and so I wonder if there is a simple voltage reducing circuit that I can either put inside, or piggy-back on top of the Fuel Tank. I imagine T-Rex would just ignore me if I sent such a request to their customer support (or at best they would recommend purchasing another T-Rex product). My electronics knowledge is not exactly impressive, but I figure it should be a fairly simple deal to reduce the voltage. Is it just a matter or adding a resistor or two? I just need a simple schematic and parts list. Can anyone help? PS. I know a lot of 9V pedals can handle 12V too, but I don't want to risk anything, so I'd prefer to get the voltage down.
many pedals work just as well with 12Vdc,mostly dynamics,you have to check out the specs in manuals to find out any problem with higher voltages.
Anyway,you can get 9Vdc easily with a 7809 voltage regulator and 4 caps from the 12Vdc output.
You can do the same with the 12Vac,just inserting a 4 diode bridge rectifier between the output and the aforementioned circuit.(more dissipated energy so you need a heatsink.)
Its everywhere,check out any site like Geofex or General guitar gadgets or Tonepad for complete projects
alexradium
Solder Soldier
 
Posts: 201
Joined: 31 Jan 2010, 14:31
Has thanked: 37 times
Have thanks: 34 times

Re: Reducing voltage from 12V to 9V on power supply

Postby tip142 » 18 Sep 2013, 19:18

alexradium wrote:
Super Locrian wrote:Hi all,

I have a T-Rex Fuel Tank Classic power supply that delivers 3 x 500 mA from three sections, 9V DC, 12V DC and 12V AC. I have exhausted the capacity of the 9V outlets (I only buy 9V pedals as a matter of principle), and so I wonder if there is a simple voltage reducing circuit that I can either put inside, or piggy-back on top of the Fuel Tank. I imagine T-Rex would just ignore me if I sent such a request to their customer support (or at best they would recommend purchasing another T-Rex product). My electronics knowledge is not exactly impressive, but I figure it should be a fairly simple deal to reduce the voltage. Is it just a matter or adding a resistor or two? I just need a simple schematic and parts list. Can anyone help? PS. I know a lot of 9V pedals can handle 12V too, but I don't want to risk anything, so I'd prefer to get the voltage down.
many pedals work just as well with 12Vdc,mostly dynamics,you have to check out the specs in manuals to find out any problem with higher voltages.
Anyway,you can get 9Vdc easily with a 7809 voltage regulator and 4 caps from the 12Vdc output.
You can do the same with the 12Vac,just inserting a 4 diode bridge rectifier between the output and the aforementioned circuit.(more dissipated energy so you need a heatsink.)
Its everywhere,check out any site like Geofex or General guitar gadgets or Tonepad for complete projects


If you haven't lying around the 7809,simply put for 1n4.... in series and you drop from 12v to 9,2 v quite happily and satisfactory.
:thumbsup
User avatar
tip142
Breadboard Brother
 
Posts: 105
Joined: 08 Nov 2009, 01:32
Has thanked: 2 times
Have thanks: 15 times

Re: Reducing voltage from 12V to 9V on power supply

Postby deltafred » 18 Sep 2013, 19:35

tip142 wrote:If you haven't lying around the 7809,simply put for 1n4.... in series and you drop from 12v to 9,2 v quite happily and satisfactory.
:thumbsup

The forward voltage drop of a 1N400x is somewhere around 0.7v so you would need 4 or 5 in series to drop around 3v.

New 9v batteries are usually a bit higher, around 9.6v so 4 should be ok but it depends how accurate your 12v supply is. If you are worried then start off with 5 and measure the pedal voltage. Take one out if it is below 9v, add another if it is over 9.6V. I would add a 100uF 16v electrolytic in parallel with 0.1 disc ceramic decoupling capacitors across the 9v output.

Not the most elegant of solutions but it will work.
Politics is the art of so plucking the goose as to obtain the most feathers with the least squawking. - R.G. 2011
Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012
User avatar
deltafred
Opamp Operator
 
Posts: 1326
Joined: 06 Apr 2010, 17:16
Location: Yorkshire, England, UK
Has thanked: 253 times
Have thanks: 221 times

Re: Reducing voltage from 12V to 9V on power supply

Postby bcalla44 » 18 Sep 2013, 22:38

Can't you do it with a 9.1 v zener diode with a resistor in series?
There are two types of people in this world, good and bad. The good sleep better, but the bad seem to enjoy the waking hours much more.
- Woody Allen
bcalla44
 
Posts: 17
Joined: 23 Jul 2011, 21:41
Has thanked: 1 time
Have thanks: 0 time

Re: Reducing voltage from 12V to 9V on power supply

Postby DrNomis » 18 Sep 2013, 22:47

I've actually seen some 9V batteries measure something like about 10V when measured by a multimeter.... :thumbsup
Genius is not all about 99% perspiration, and 1% inspiration - sometimes the solution is staring you right in the face.-Frequencycentral.
User avatar
DrNomis
Old Solderhand
 
Posts: 6856
Joined: 16 Jul 2009, 05:56
Location: Darwin,Northern Territory Australia
Has thanked: 123 times
Have thanks: 383 times

Re: Reducing voltage from 12V to 9V on power supply

Postby deltafred » 18 Sep 2013, 22:54

bcalla44 wrote:Can't you do it with a 9.1 v zener diode with a resistor in series?

You can but you waste more power because you need a certain current through the zener for it to operate properly (and 9v batteries don't have a lot to waste).

With the 1N400x you only draw the current the pedal draws, a zener needs a few milliamps extra.
Politics is the art of so plucking the goose as to obtain the most feathers with the least squawking. - R.G. 2011
Jeez, she's an ugly bastard, she makes my socks hurt. I hope it's no ones missus here. - Ice-9 2012
User avatar
deltafred
Opamp Operator
 
Posts: 1326
Joined: 06 Apr 2010, 17:16
Location: Yorkshire, England, UK
Has thanked: 253 times
Have thanks: 221 times

Re: Reducing voltage from 12V to 9V on power supply

Postby mictester » 19 Sep 2013, 00:21

bcalla44 wrote:Can't you do it with a 9.1 v zener diode with a resistor in series?


You can, but the resistor will just be wasting energy as heat! Also, zener diodes tend to be a bit noisy.
Everything gets easier with practice, except getting up in the morning!
User avatar
mictester
Old Solderhand
 
Posts: 2852
Joined: 11 Sep 2008, 21:29
Location: In the hills of North London
Has thanked: 32 times
Have thanks: 762 times


Return to Power

Who is online

Users browsing this forum: No registered users and 1 guest