My pro inkjet can print onto thick card, canvas and CDs, but whilst the ink is permanent on photo paper it is not always the case with other mediums, I suspect that printing direct onto copper clad board would just see it wash off in the etching bath.

 

I don't get what U3's function in the circuit is, if someone could explain that would be great.

 

I don't get what U3's function in the circuit is, if someone could explain that would be great.

It makes the negative supply track the positive.

 

I have been looking for a Dual Tracking Power Supply circuit to build and the schematic below was recommended as an upgrade to a circuit on the JoeBrown.org.uk website. I understand the schematic was designed by Harry Brunts.

View attachment 122040

The OpAmp's tested have been either an LM108 or an LF351 but as I don't have either of those to hand could I use a different type?

I've got available: RC4136N, TL071, 072, 074, 082, NE5532P, LM833N, LM1458N, LM358P & 4560D, which of these would be the best match for this circuit? If one of these are used would I need to change anything else to get a similar end result (perhaps need a different regulator than the 78L08)?

I have almost everything required apart from the 15-0-15 50VA Transformer, but I do have a 18-0-18 50VA Transformer. All the Electrolytics will be 50V versions aside from the two 4700uF which are only 35V. I have the 4 resistors required as 1W 1% and have selected those closest to the required values, the two 10K resistors are both identical giving the same readings on each of my meters.

I have lots of 1N4001s, 1N4003s & 1N4007s so will use 1N4007s for the six diodes.

I cannot find a C2, has the author just miss counted or should there be another Capacitor in there somewhere?

Hoping you can advise, you have given me good advice to date so looking for more.

With a few quibbles it looks ok. You can't use a LM833N op amp as they are not stable with unity gain. Also the TL series is not ideal for this - they have a low source or sink current - I forget which. They are otherwise a favourite of mine for jelly-bean applications. One other thing is the +8 and -22 volt supply may be a bit close to the maximum rating for the op amp. If you have grief maybe replace the -22v supply to the op amp with something like a -8v regulator (it isn't too fussy -5 to -15 should all work about the same - just check the pinout, it is different to the +ve regulators.

As has already been mentioned you have a minimum voltage of +1.25 not zero. With the 120 ohm resistors in place to keep minimum regulating current I would use the NE5532P for the op amp.

 

Just seen the extra replies to my thread. Thank you for your input, the circuit has been built for some time and works admirably.

 

This looks very nice indeed, you done an excellent job.

I am seriously thinking of attempting this myself.....

what is the available current from each rail?

 

Is the last circuit a correct and working example?

 

What?..... nobody has any answers?

Thought you guys were smarter than that.....

 

Thread has been silent for over 10 months. TS might have moved on. The sch in post #34 looks ok.

ak

 

So I can hook up my transformer to where is says +18 and -18?.... I have a split 12-0- 12 transformer so my output will be a little lower which is fine.

 

Correct.

Not shown on the schematic is that the left side of R2 connects to GND. U3 is acting as a DC servo to drive the negative output to whatever it takes to make the junction of R6-R7 be at GND. C4 and (R6 and R7 in parallel) set the frequency response / response time of the servo to a transient unbalanced load current.

Search for tracking power supply schematic to see other variations on the theme.

ak

 

Correct.

Not shown on the schematic is that the left side of R2 connects to GND. U3 is acting as a DC servo to drive the negative output to whatever it takes to make the junction of R6-R7 be at GND. C4 and (R6 and R7 in parallel) set the frequency response / response time of the servo to a transient unbalanced load current.

Search for tracking power supply schematic to see other variations on the theme.

ak

The output from my transformer is AC....I can put that direct into the LM317?

 

Nope. Bridge and filter capacitors. This thread discussed the regulator only, not the front end.

ak

 

Here's a triple-output supply, using LM317's and LM337's, with a single positive output, and a tracking plus and minus output that can all be adjusted to zero volts.
It's handy to have the single output for powering logic circuits, and the dual outputs for analog circuits.

 

Here's a triple-output supply, using LM317's and LM337's, with a single positive output, and a tracking plus and minus output that can all be adjusted to zero volts.
It's handy to have the single output for powering logic circuits, and the dual outputs for analog circuits.

That's a nice supply....Do you happen to have a link to a function generator schematic, square and sine wave from 0.1Hz to 20Khz?

I'm thinking maybe I could house the two projects in one box?

 

.Do you happen to have a link to a function generator schematic, square and sine wave from 0.1Hz to 20Khz?

Sorry, I don't.
You'll have to try the old Google shuffle.

 

DDS modules are cheep.