Group Actions
Engagement
  • Author Author: Robert Peter Oakes
  • Date Created: Date Created
  • Views 3796 views
  • Likes 3 likes
  • Comments 14 comments
Related
Recommended

Voltage References - The Modular Bench Power Supply ++

Robert Peter Oakes

To Main Blog: The Modular Bench Power Supply ++, The Essential DIY Build for Every EE Student and Old Timer alike...

 

Every good power supply depends on a good voltage reference, it provides the anchor to keep everything stable and performing well and accurately

 

Without a good voltage reference, your supply will drift over time, with temperature changes and if the supply voltage changes even a little, not to mention noise that can be introduced by outside sources

 

What I will show you over the following two videos is a bit of theory and a practical demonstration of how the above things can interfere with the workings of the reference and therefor the rest of the power supply

 

I will exaggerate the problems by using a hot air soldering gun, an Arbitrary Waveform Generator and significantly changing the source voltage for the reference circuit

 

I will only show 3 variations which should represent the most popular techniques

 

A Zener Diode 3V _+ 5%

A Zener Diode with a JFET constant current source and an offset silicon diode to assist with temperature stabilization

A Silicon Chip reference device (REF02 in this case from TI but this is one of dozens of choices available) that outputs a stable 5.000 Volts

 

First up the theory:

 

Now time to turn up the heat... Literally image

 

These are the circuits I used in the above videos, the video used a bread board, the circuits are assuming a plug in module but the circuit is the same either way

image

 

Conclusion

USE A REF02 OR SIMILAR DEVICE, ITS NOT WORTH THE HASTLE OF THE ALTERNATIVES

 

If you disagree, lets hear it, this is just my opinion and I would love to hear yours

 

 

BOM

REF02 http://canada.newark.com/analog-devices/ref02hsz/ic-series-v-ref-5v-25mv-8-soic/dp/59K9016  $3.53

Zener BZX79-C3V0 NXP Diodes - Zener Single | 96K7357 | Newark element14 Canada  +  $0.177

Resistor  $0.10

Diode      $0.216

So yes the REF02 is significantly more expensive but were still talking under 4$ for the part and watch the video to see the rest

 

In the next video we will look at OP AMPS and how we can use them to help control our circuits

  • in reply to Former Member

    If i remember correctly the 5V from the generator was capacitivly coupled, therefor the 20V from the POWER side will not harm the reference

     

    one other way I have connected the this int he past is to "Stand" the 5V signal on the power rail (In series to the 20V) producing an addition to the main supply. As the Generator output is isolated this is perfectly safe and a reliable way to inkect a "Noise", Ripple" signal. The OP-Amp and Vref does not consume much power so the generator is more than able to supply it. it is of course not supplying the main output of the power supply, just to the control components

  • Hi Peter,

     

    Thanks again for the wonderful videos. Please excuse my ignorance, and also the fact that this is not the main topic in your presentation, I thought a while, but could not figure out how you are connecting the power supply and the signal generator to test the v. references. I could be totally mistaken here, but I thought you had mentioned that the ground leads of the two instruments are connected, in which case the 20V potential on the output of the p.sup. should drive some current into the signal generator oscillating at 5 V p-p. If the two are connected in series, then the same current should go through both of the instruments. What is the point I am missing here?

    I am assuming here that a p.sup or a signal gen. should not be connected to a circuit that in itself has a voltage source, maybe here I am mistaken.

     

    Regards, Gilbert

    p.s. I am studying the op amps videos, you are going through an actual hands-on design and build procedure in detail, which is unique and great.

  • in reply to mcb1

    If there are communication problems on the site they usually aren't because of the spellings. The main concern is: Does one understand what is being said? Peter does and excellent job of conveying his meanings in his writing and speaking.

    John

  • in reply to Robert Peter Oakes

    I was looking forward to implants. image

     

    The website forces us to use the american spelling for everything, so my entries are often wrong ...

     

    Mark