Help me understand the Micro Vibe

[antonis]

It's just a power supply ripple voltage reservoir cap..
It could do better job (just like C11 does for +4.5V supply) if a relatively small value resistor was placed between D3 cathode & cap positive plate..)

For 18V, its voltage rating must be raised up to 25V..
Its capacity has nothing to do with supply voltage but a lot to do with supply current..
(you can see C11 been more than ten times smaller 'cause it has to smooth much less current..)

[jlo]

So assuming the caps are rated 25V, what would you change in the power supply section to run at 18V.  So if the TL062 has a current draw of 200uA  vs TL072 1.5mA vs OPA2604 10.5mA  that would affect the value you would use? 

[antonis]

Without any info about new power supply, I shouldn't change anything at all..
I should raise R31 value up to 2k2..
I should change that  C15 tantalum cap with an electro at any cost..
(or even better, I should get rid of the whole by-pass configuration..)
I should add 100nF ceramic caps as close as physically possible between pins 8 & 4 for each of U1, U2 & U3..


But shouldn't be more convenient to start a new thread about power supply basics..??

[jlo]

Wasn't sure if I should start a new thread for each question... I can change this if the mods feel like i should

Power supply is Dunlop 18v 500mA

I did add caps to each opamp

Why change C15? 

[antonis]

Why change C15?

Because it's my personal habbit to hang around with a desoldering pump desperately looking for a tantalum cap..!!
(and a cut plier for browbeating the tough ones)

[jlo]

So with an 18V 500mA power supply and 40mA bulb and OPA2604s would c13 or c11 need to be changed? 

[antonis]

Maybe yes, maybe no..
(it stricktly depends on power supply regulation specifications..)

I let you calculate total circuit current requirement, take in mind worst case scenario (e.g. mains lower amplitude), determine your PS total circuit configuration (e.g. simple full-wave rectifier with a reservoir capacitor of known(?) value or the former followed by linear regulator with appropriate caps) and decide if respective caps need to be changed..

P.S.
I'd suggest you to study power supply basics, 'cause if you don't, you'll keep coming for any slightly different case of the one already answered/pointed (but not understood..)

[jlo]

Maybe yes, maybe no..
(it stricktly depends on power supply regulation specifications..)

I let you calculate total circuit current requirement, take in mind worst case scenario (e.g. mains lower amplitude), determine your PS total circuit configuration (e.g. simple full-wave rectifier with a reservoir capacitor of known(?) value or the former followed by linear regulator with appropriate caps) and decide if respective caps need to be changed..

P.S.
I'd suggest you to study power supply basics, 'cause if you don't, you'll keep coming for any slightly different case of the one already answered/pointed (but not understood..)

Will definitely do some reading.  Thx.  The specs on the power supply say 5% regulated.  Not sure what that means.  Is that 18v +/- 5%?