charge pump voltage divider issues?

[karsten_h]

hi out there...

i did set up a roadrage circuit on my breadboard and it seems to work fine although the voltages are a little lower as expected. i feed in around 8,74V from the wallwart. after D1 8,44V remain and i get like -8,17V at pin5, after D3 it reads12,62V, after D4 16,09V and 14,8V at the output of the regulator.

so i wanted to feed a little more voltage around 9,6V from another wallwart that gives 12V and grab them from a voltage divider i calculated and did set up aswell. seems to wirk fine.

but when i feed the 9,6V from there into the roadrage circuit the voltage drops to 2,7V??? any idea what happens there?

[antonis]

Your voltage divider Vout is calculated with NO LOAD..!!
(i.e. No extra current flowing through R1 hence no extra voltage drop across it..)

With a brute approximation, Vout load in parallel with R2 equivalent resistance should be about one third of R1..

[karsten_h]

thx, i thought that the circuit load would do something to the calculations but what would that mean for a newbee to do now? something like this?

[antonis]

thx, i thought that the circuit load would do something to the calculations but what would that mean for a newbee to do now?

To estimate/calculate circuit current draw and lower R1 & R2 values accordingly..
In case you have a fixed current draw, you may omit R2..
In case of variable current draw, make R1/R2  equivalenbt resistance (their parallel combination) 1/10 (or lower) of circuit resistance..

Make R1 100R and R2 470R but beware of their power rating..

P.S.
More practically, use a 7810 voltage regulator (hoping for 2V IN-OUT dropout to be OK..) or implement a series BJT with its Base biased at about 10.2V..
https://www.elprocus.com/transistor-series-voltage-regulator/
https://electronics.stackexchange.com/questions/625280/series-voltage-regulator-with-zener-diode-and-bjt-equations-to-explain-the-wor
For a precise Vout, I'd use a 12V Zener with a voltage divider to BJT Base..

[karsten_h]

guess the charge pump can hanle 100mA so what wattage do i need for the resistors?

[antonis]

Resistors wattage should be rated according to current flowing through theirselves..

If your DMM has not current measure mode, place 1 to 10 Ohm in series with the circuit and measure voltage drop across it..
(from your voltage divider output domnination, I'd say around 20mA but better be sure..)

P.S.
Voltage division via resistive divider is a current hungry and power consumption configuration..

[karsten_h]

hi out there...

i did set up a roadrage circuit on my breadboard and it seems to work fine although the voltages are a little lower as expected. i feed in around 8,74V from the wallwart. after D1 8,44V remain and i get like -8,17V at pin5, after D3 it reads12,62V, after D4 16,09V and 14,8V at the output of the regulator.

https://www.freestompboxes.org/viewtopic.php?t=32702

actually it seems i did no wrong but the configuration of the roadrage circuit is as it is and lacks something... because i do not need the 18v/15v configuration right now i get rid of all that stuff and strip the circuit down which gives me -8,59V which is not a brandnew battery - but ok.

[antonis]

Neither charge pumps nor voltage doublers are flawless items/configurations but not so troublesome..!!

Try your 12V -> voltage divider -> road rage with no load connected to see what voltages you get..

 

[karsten_h]

implement a series BJT with its Base biased at about 10.2V..
https://www.elprocus.com/transistor-series-voltage-regulator/
https://electronics.stackexchange.com/questions/625280/series-voltage-regulator-with-zener-diode-and-bjt-equations-to-explain-the-wor
For a precise Vout, I'd use a 12V Zener with a voltage divider to BJT Base..

would like to learn more about this... when i work with the 8,74V wallwart as supply i can set up something using a 9,1V zenner (i have at hand) and a BJT (have several here...) can you suggest what would work here? to get something like <-9V for example?

[antonis]

when i work with the 8,74V wallwart as supply i can set up something using a 9,1V zenner (i have at hand) and a BJT (have several here...) can you suggest what would work here? to get something like <-9V for example?

Unfortunately, no..

Zeners work as voltage regulators/stabilizers but they need a voltage higher than their nominal breakdown voltage..
https://en.wikipedia.org/wiki/Zener_diode

[antonis]

You can use a 78L10 regulator with 12V wallwart supply and a Schottky diode (e.g. 1N5817) for about 9.7V or a Silicon rectifier diode (e.g. 1N40XX) for about 9.4V..

[karsten_h]

figured out that with R2 560ohm 1/4W and R1 100ohm 1/4 W i have -9,21V that´s pretty much what i wanted... WITHOUT LOAD! when i add leds and 510ohm resistors to the +/- outputs voltage drops about 3V is that what it is? the wallwart is from an old speedport router 12V 1,25A 15W max that should be enough...

[antonis]

when i add leds and 510ohm resistors to the +/- outputs voltage drops about 3V is that what it is?

You aren't suprised anymore, are you..??

[karsten_h]

guess i´m not...
someone suggested to use a LM317 and set it to the desired Vin (https://praktische-elektronik.dr-k.de/Bauelemente/Be-LM317.html)

[antonis]

Let's do some homework..

Calculate Vout for SW1 & SW2 open, SW2 closed & SW2 open and SW1 & SW2 closed..

[antonis]

someone suggested to use a LM317 and set it to the desired Vin (https://praktische-elektronik.dr-k.de/Bauelemente/Be-LM317.html)

Expensive solution..

A 78L10 regulator and a 2N3904 (or any other equivalent BJT) should serve for your purpose..



P.S.
Could you plz post a schematic of what exactly you power with bi-polar supply..??

[karsten_h]

thx for bringing me thru this...

#1: Vout=10,18V
#2: RF=267ohm, Vout=8,73V
#3: RF=175ohm, Vout=7,63V

[karsten_h]

someone suggested to use a LM317 and set it to the desired Vin (https://praktische-elektronik.dr-k.de/Bauelemente/Be-LM317.html)

Expensive solution..

A 78L10 regulator and a 2N3904 (or any other equivalent BJT) should serve for your purpose..



P.S.
Could you plz post a schematic of what exactly you power with bi-polar supply..??

LM317: 0,36€
78L10: 0,27€










the circuit is going to give power to my circuit testing/breadboarding setup. first thing to breadboard when i have negative voltage would be rangemaster/tonebender/zonk/jhs treble booster circuits with positive ground. thought that biasing the circuits would make more sense with a power close to what a good battery would supply what do you think?

[antonis]

LM317: 0,36€

Fair price for counterfeit..

[karsten_h]

LM317: 0,36€

Fair price for counterfeit..

... think so?

https://www.musikding.de/LM317T
https://www.banzaimusic.com/search.php?mode=search&page=1&keep_https=yes