I think you need to consider DC and AC separately. I'm WAY off being experienced enough to guide you through it myself, I still end up wearing the dunces hat way too often, but I think you need to see the voltage after your transformer and presumably a fullwave or bridge rectifier as DC + AC ripple. The DC you can use ohms law on as has been said. The AC ripple wil be smoothed by the CLC. I find it useful to think of both.
PSUD is a very useful PC program for your initial PSU design and will get you in the right ballpark, though as you say building and measuring will bring it home.
PSUD is a very useful PC program for your initial PSU design and will get you in the right ballpark, though as you say building and measuring will bring it home.
Hi Ben
Yes thats correct . It’s a suppose to be a CLC . I just rig this up to test. The series resistor is shorted to the ground as load. Right now just want to see if it works .
Thks
Yes thats correct . It’s a suppose to be a CLC . I just rig this up to test. The series resistor is shorted to the ground as load. Right now just want to see if it works .
Thks
Hi RhythMick
Yes measures dc & it reads almost 17v . Ac is 12v. I use to muck around with chokes back when I was building some tube preamps & what I found was somehow there seems to be something missing using Ohms Law when Chokes are concern. Perhaps I wasn’t that experience then but ????
Thks
Yes measures dc & it reads almost 17v . Ac is 12v. I use to muck around with chokes back when I was building some tube preamps & what I found was somehow there seems to be something missing using Ohms Law when Chokes are concern. Perhaps I wasn’t that experience then but ????
Thks
Chokes follow Ohm's Law quite accurately for DC. AC complicates things, but not in the case of the choke in a CLC arrangement.
Be aware that to get measurements you have to combine raw data (what the meter tells you) with correct understanding; people often say they have measured something but in fact they have measured something else because their misunderstanding led them astray.
Be aware that to get measurements you have to combine raw data (what the meter tells you) with correct understanding; people often say they have measured something but in fact they have measured something else because their misunderstanding led them astray.
So where have I gone wrong with this simple test DF96 ?
Indeed when I think back, when the value of the choke is high
& if not loaded correctly , you definately will get 0v at the output
but strangely I getting a reading here.
Indeed when I think back, when the value of the choke is high
& if not loaded correctly , you definately will get 0v at the output
but strangely I getting a reading here.
I think you should start again, working backwards from the load.
What DC voltage do you need?
What current draw are you expecting?
What ripple voltage (AC) is acceptable?
The current draw through the CLC filter will tell you what drop in voltage to expect across it (ohms law, DCR * current) and therefore what voltage you need after the bridge,which will itself have a small voltage drop therefore giving your transformer requirement.
The LC filter will give a ripple smoothing factor which will tell you what ripple to expect at the load.
What DC voltage do you need?
What current draw are you expecting?
What ripple voltage (AC) is acceptable?
The current draw through the CLC filter will tell you what drop in voltage to expect across it (ohms law, DCR * current) and therefore what voltage you need after the bridge,which will itself have a small voltage drop therefore giving your transformer requirement.
The LC filter will give a ripple smoothing factor which will tell you what ripple to expect at the load.
Thanks again RhythMick. Expecting to see around 11-12v at output of Choke. Current draw is around 90-100 ma on the shunt regs that Im using now. This choke thinggy is out of the box thinking that I would like to test on low voltage application. Will work on it & do further test.
We have no idea what you have actually done so no idea what you should have seen. The story keep changing. First the choke was "across" the supply, then in series. Now a shunt reg has appeared. Current draw is described as 90mA, yet that is impossible with the choke in series. You need to take a deep breath and stop experimenting and start thinking. Show us exactly what you have done (a diagram helps us think, a photo helps us see whether you have actually done what you say you have done - so we need both).
Come on DF96 across would definitely be in series. Since when have you seen a choke connected otherwise. When I said shunt regs it is meant that my plans was to connect this to a shunt reg that draws around 90ma. Besides it does not matter what Im connecting the supply too as long as we know what the current draw is right ?
No, "across" means shunted across the output of the PSU. Newbies connect things in strange ways, so experience has taught me not to dismiss as impossible some daft connection.
As I said, if you want help with Ohm's Law you need to show us exactly what you did.
As I said, if you want help with Ohm's Law you need to show us exactly what you did.
Well looks like we’ve got a little miscom DF96. Early days when I built some kits manuals description of across is in context of series connection & not shunt. In anycase this would have been clear to you given you experience. This is what Im doing off course cap values are there just for testing.
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"Across" means shunt.
What you have done is completely unclear to me, because of my experience. It is my experience which has taught me to distrust what people say when they say they are telling me what they have done; daft results often mean that they have done something different. The lack of knowledge which makes them wire things wrongly also makes them misdescribe what they have done.
You now appear to have a 4 ohm load on a PSU with an internal resistance exceeding 210 ohms. It is unclear what you expected this to do.
What you have done is completely unclear to me, because of my experience. It is my experience which has taught me to distrust what people say when they say they are telling me what they have done; daft results often mean that they have done something different. The lack of knowledge which makes them wire things wrongly also makes them misdescribe what they have done.
You now appear to have a 4 ohm load on a PSU with an internal resistance exceeding 210 ohms. It is unclear what you expected this to do.
If you saw the picture that I post with Dvm readings , yes I use a 4R resistor as a dummy load. I also did a test with a 470R resistor & that too give me a reading but voltage was down to 10.45 v or so.
@sumotan - if you are using PSUD2, why would you select 4R as the load? Why not use a current sink with the expected current, and find out the exact voltage drop across the inductor? Or do you just like to waste your own and the others' time? 🙂
For those following along at home.... the extremely odd values used do not compute correctly in PSUD-II. PSUD is intended for "reasonable" combinations of values. It uses good approximations for "normal" sets of values. If you set up Ben's interpretation of sumotan's postings, voltages do not add-up around the L-C-L loop.
Also the *actual* test shown in sumotan's picture is not L-C-L and there is no good way to set up a a C-L-R filter. Making C2 very small leads to impossible answers or a PSUD blow-up.
Also the *actual* test shown in sumotan's picture is not L-C-L and there is no good way to set up a a C-L-R filter. Making C2 very small leads to impossible answers or a PSUD blow-up.
What I had shown in post #10 was not my interpretation of sumotan's circuit. I was trying show sumotan a more reasonable solution to provide the power that he wants.
The choice of a 210 ohm dcr choke is not going to work for what he wants out of the circuit, and practically everyone is aware of that.
By the way, the numbers of that simulation do not seem to add up probably because of the mean voltages being skewed by the turn-on surge.
The choice of a 210 ohm dcr choke is not going to work for what he wants out of the circuit, and practically everyone is aware of that.
By the way, the numbers of that simulation do not seem to add up probably because of the mean voltages being skewed by the turn-on surge.
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Your MATH is innaccurate (just to say it politely 🙄), 90mA through 210 ohms means a 18.9V voltage drop ... higher than what your supply voltage.
Explain THAT, genius. 🙄
Do you think you will find Ohm´s Law does not apply?
Impossible.
A 210 ohm /4 ohm voltage divider, with 17V input, will give you (4/214)*17=0.32V DC
Of course, maybe you don´t know how to measure, your meter is out of batteries or you are trolling us.
Try "everything wrong" and you´ll be close.
Cool, but you´ll learn nothing if you close your ears to error correction.
Otherwise what´s the point?
Why ask here at all?
Ohm´s Law applies at ANY voltage.
You should have learnt that in your earlier experiments, or they were a waste of time.
Our combined experience is telling us you are WRONG.
So a 470 ohm load caused output voltage to drop to 10.45V but a 4 ohm one (120 times heavier load) ONLY made it drop to 12.7V??????? 🙄🙄🙄🙄
No, he's right. He asked an odd question, and his meter gave the correct answer for what he asked.
Look carefully at post #19. He found 12.4V across the choke.
I have _NO_ idea why he measured across the choke. The choke is the crap we want to throw away. We want a clean Load. We would normally measure the load voltage. That's the part we want to use.
But yes, for the connections semi-clearly shown in post #19, he gets the "huge drop" that everybody else has said.
First image shows what _I_ thought he wanted to do. The LOAD gets 6V DC. The first-cap voltage is about 13V DC with 1V AC. The AC is "small". For a first approximation we can use only DC voltage-dividers and get a good answer. The "171r" was an early guess; in fact as someone pointed out earlier there is NO way to get the 90mA in any load if the raw AC is 12V and the choke has 210 Ohms in it.
Second image (incorporating the #19 picture) reenacts the picture in #19. We indeed get 12.4V where the probes are put. Across the choke. The first-cap raw DC runs 12.7V. The load gets 0.235V.
There is of course no way to get "11-12v ...90-100 ma" with 12VAC rectified to ~~17VDC and a 210 Ohm choke.
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