Using the Coarse + Fine Control circuit in my new Dual Bench Supply

RE: Using the Coarse + Fine Control circuit in my new Dual Bench Supply

Workshopshed — Tue, 13 Jun 2017 14:47:44 GMT

Fantastic project, very professional result

RE: Using the Coarse + Fine Control circuit in my new Dual Bench Supply

mcb1 — Fri, 03 Feb 2017 07:03:31 GMT

Nice work.

I can recall the amount of time we spent in the old days designing supplies, and then having to remove all the self oscillation, etc.

Using these modules gets you a very good, stable enough source for general purpose use.

Mark

RE: Using the Coarse + Fine Control circuit in my new Dual Bench Supply

the-dubster — Wed, 01 Feb 2017 08:36:58 GMT

Dammit John, now I've got to go and dig out that meaty toroidal transformer I've been storing for the last few decades . . . . .

To be honest, I've (so far) not been disappointed by the cheap eBay modules I get from China, my LCR/Semiconductor meter I bought for the pricely sum of just under £12 gbp does well enough for me too.

Nice mod with the current shunts too! [View:/resized-image/__size/16x16/__key/commentfiles/f7d226abd59f475c9d224a79e3f0ec07-e177bc30-fcec-44fe-900e-da3439f5689d/contentimage_5F00_930.png:16:16]

RE: Using the Coarse + Fine Control circuit in my new Dual Bench Supply

gbrettell — Wed, 25 Jan 2017 04:29:25 GMT

Great job!

The front panel is laid out really well ... looks good.

RE: Using the Coarse + Fine Control circuit in my new Dual Bench Supply

D_Hersey — Tue, 24 Jan 2017 23:55:43 GMT

Analytically, we can group the op-amp and Rfeedback. Then we have a transresistance (aka transimpedance) amplifier

https://en.wikipedia.org/wiki/Transimpedance_amplifier

RE: Using the Coarse + Fine Control circuit in my new Dual Bench Supply

D_Hersey — Tue, 24 Jan 2017 23:24:43 GMT

I forgot to discus the feedback resistor, of course you pick it to scale the inputs, remembering that the fixed resistor, if it is any good, probably drifts less than the variable ones, for a given amount of power

RE: Using the Coarse + Fine Control circuit in my new Dual Bench Supply

D_Hersey — Tue, 24 Jan 2017 23:16:26 GMT

John, hi! Your control circuit is baffling me, not that it takes much these days, too bad about the Packers.

What if we took a smaller and larger pot, something like a 10:1 ratio, although 5:1 and 2:1 are possible, we could even use 1:1 if we threw a fixed resistor in series with the trimmer? Let's degenerate them into variable resistors the common way by busing the wiper with one end of the resistor. Let's knit our brows then pronounce them variable conductors. We attach one end of each of our variable conductors to a high reference potential. Let's attach the free ends of these conductors to the summing (inverting terminal -- virtual ground) junction of an op (summing amplifier) amp with the non-inverting input held (matching the input Z's with an R to mitigate current drift) at a lower reference potential

Wouldn't this give you the linearity you are seeking?

Un-knit now

Hoping you and your family are fine!

RE: Using the Coarse + Fine Control circuit in my new Dual Bench Supply

DAB — Tue, 24 Jan 2017 22:45:35 GMT

Great build John.

I like the idea of reusing older technology and then brining it up to par with new devices.

Well done.

DAB

RE: Using the Coarse + Fine Control circuit in my new Dual Bench Supply

balearicdynamics — Tue, 24 Jan 2017 09:26:18 GMT

You have done a very good job. And it's a great project. I think to copy and make one of these in the near future for a project that may arise next months.

Enrico

RE: Using the Coarse + Fine Control circuit in my new Dual Bench Supply

rachaelp — Tue, 24 Jan 2017 07:48:13 GMT

That's a nice tidy looking bench PSU!

Have you tested it out with various loads and looked at how well the cheap regulators are working? Is there switching noise on the outputs? If that's the case then something you could do to kill two birds with one stone is to put a linear reg on the output to clean it up. So you'd set your DC-DC converter so that at it's lowest setting it's voltage was high enough headroom to go into a linear regulator for lowering to the final output without causing too much heat dissipation in the regulator. This will likely enable you to get your output close to 0V too depending on how you do it.

Best Regards,

Rachael