Voltage Regulator question

[Govmnt_Lacky]

I want to incorporate a 15V 1A voltage regulator (7815) into an M-117 Flanger design.

Can I just solder the regulator onto the DC input jack and run a wire from the regulator output to the Board's input?

Does the regulator need any kind of filtering (i.e. capacitors) before or after it's input power?

This is the first time I will be incorporating a voltage regulator that is not already part of the circuit and could use some guidance.

Thanks for the help 

[merlinb]

It is good practice to put a 0.1uF ceramic cap at both input and output of a regulator IC, physically close to it. A larger input cap (few tens of microfarads) is also recommended in addition to the 0.1uF since you'll have a long cable feeding the raw DC input. The 0.1uF at the input is the most important.

Some people add a large cap at the output too, but this is emphatically not recommended as it retards regulation. Anything over 10uF is unnecessary here.

However, if you're really stuck for space then you'll probably get away without all these things! Depends how "professional" you want to be.

[Govmnt_Lacky]

Thanks Merlin. I am really concerned with protecting the coveted SAD1024 chip. I knew about the 100uF cap and even a polarity protection diode but I was not aware of the 0.1uF caps.

[petemoore]

  Polarity LED/resistor or DMM to test for sure polarity is understood before applying it ! !
  I like to get it straight and then hardwire it and then check that I hardwired it correctly [jack/plug or anything that keeps the polarity correct].
 

[Govmnt_Lacky]

  Polarity LED/resistor or DMM to test for sure polarity is understood before applying it ! !
  I like to get it straight and then hardwire it and then check that I hardwired it correctly [jack/plug or anything that keeps the polarity correct]. 

Sorry but I have no idea what this post has to do with the thread. Could you please elaborate on what you mean?

[greaser_au]

It is good practice to put a 0.1uF ceramic cap at both input and output of a regulator IC, physically close to it. A larger input cap (few tens of microfarads) is also recommended in addition to the 0.1uF since you'll have a long cable feeding the raw DC input. The 0.1uF at the input is the most important.

Years ago I found some of these things can oscillate without the decoupling capacitors...

Some people add a large cap at the output too, but this is emphatically not recommended as it retards regulation. Anything over 10uF is unnecessary here.

Agreed!   Further, the specs say that in all cases Vin should be greater than Vout.  Of course,  this is what happens in normal conditions!  However, if the input side filter caps are drained (say by a short, or a heavy load) faster than a large cap on the output side it can destroy the device.

david

[Govmnt_Lacky]

After some email banter back-and-forth with TI, I was sent this about the LT1054CP voltage doubler circuit:

"I just confirmed with specification team. The maximum  output current of 100mA also applies to VIN=9V. Let me know if you have further specfic questions or feedback..

Naser Salameh
Texas Instruments
Semiconductor Technical Support"

I am going to get some more confirmation about this but it appears that it will handle the 50-75mA draw of the M-117 Flanger circuit. Unlike the MAX1044.

[PRR]

> Can I just solder the regulator onto the DC input jack

I just bolt 7805 to the back of the dashboard.

The fuel gauge in some older cars/trucks needs "constant" voltage. In the 1930s this was a heater and thermostat to chop-drop "6.3V" (5.5V-7.5V) to something averaging near 5V. The same part was used into the 1970s.... on "12V" systems it chopped more and still gave 5V average.

The fuel gauge in the old mail-van was reading low even when full. It was hard to meter the chop-wave but maybe 3V average. The auto-parts store probably had or could-get one, but that meant driving. I had 7805 in hand. I soldered the caps to the legs, fit the heatsink/ground tab to the old regulator's screw, worked fine.

[Govmnt_Lacky]

> Can I just solder the regulator onto the DC input jack

I just bolt 7805 to the back of the dashboard.

The fuel gauge in some older cars/trucks needs "constant" voltage. In the 1930s this was a heater and thermostat to chop-drop "6.3V" (5.5V-7.5V) to something averaging near 5V. The same part was used into the 1970s.... on "12V" systems it chopped more and still gave 5V average.

The fuel gauge in the old mail-van was reading low even when full. It was hard to meter the chop-wave but maybe 3V average. The auto-parts store probably had or could-get one, but that meant driving. I had 7805 in hand. I soldered the caps to the legs, fit the heatsink/ground tab to the old regulator's screw, worked fine.

Thanks Paul.

I don't think that it will require heat sinking the 7815. The circuit supposedly only draws 75mA max. I am even contemplating using a 78L15 since it can handle up to 100mA.