Hi all,
So I'm NEW to building electronics - so thanks in advance for your patience with me haha.
I bought this with the 2.5" heatsink option and 12vdc output.
I rolled up the voltage from 0-18vac and cannot get a clean 12vdc output voltage on it. What am I missing here?
Here's a photo off the scope:
So I'm NEW to building electronics - so thanks in advance for your patience with me haha.
I bought this with the 2.5" heatsink option and 12vdc output.
I rolled up the voltage from 0-18vac and cannot get a clean 12vdc output voltage on it. What am I missing here?
Here's a photo off the scope:
An externally hosted image should be here but it was not working when we last tested it.
Your input voltage is likely not high enough at all times. The lowest point of the input
voltage ripple must be higher than the minimum input voltage spec of the regulator,
plus a safety factor to allow for line voltage variation.
voltage ripple must be higher than the minimum input voltage spec of the regulator,
plus a safety factor to allow for line voltage variation.
I rolled it all the way up to 24vac, with no improvement in the ripple - I think it worsened slightly in fact.
Can you try a DC voltage for the input instead? Are all the components installed in the correct polarity?
Especially check the diodes and resistors on the regulator.
Especially check the diodes and resistors on the regulator.
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Does the ripple look like a sine wave, a rectified sine, or more triangular? What frequency is it?
Hi Yannie,
The board looks fine but your method of testing it seems a bit chaotic. It is common for those just starting with electronics.
All we can see are some curves that look like something that does not belong on a simple voltage regulator board.
The regulator chip is most likely an LM317 (please check by looking at the marking on it).
Next, try for a start with a resistive load (at the output) which draws some 20mA. What output voltage is your board set for?
Then, take the probe from your very nice scope and put the ground clip to "GND" on the output. The probe tip you connect to the positive terminal of C5.
Let us see how the voltage there looks (DC setting of the scope and a photo of the oscilloscope screen only so we can see the small writing on the scope).
12Vac at the input for a start.
The board looks fine but your method of testing it seems a bit chaotic. It is common for those just starting with electronics.
All we can see are some curves that look like something that does not belong on a simple voltage regulator board.
The regulator chip is most likely an LM317 (please check by looking at the marking on it).
Next, try for a start with a resistive load (at the output) which draws some 20mA. What output voltage is your board set for?
Then, take the probe from your very nice scope and put the ground clip to "GND" on the output. The probe tip you connect to the positive terminal of C5.
Let us see how the voltage there looks (DC setting of the scope and a photo of the oscilloscope screen only so we can see the small writing on the scope).
12Vac at the input for a start.
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Yes - I've been learning just fast enough to not blow up my scope haha (note the new differential probe, which is offering me some wiggle room on slapping a probe on wires a little unknowingly of things like ground isolation, etc).
I'll confirm the chip, which is regulating the 120vac an output voltage of 12VDC.
I'll set up the scope as you've mentioned above and share a screenshot shortly.
Thanks for the help, all... I love forums - so amazing to have this sort of help when you're just getting started.
I'll confirm the chip, which is regulating the 120vac an output voltage of 12VDC.
I'll set up the scope as you've mentioned above and share a screenshot shortly.
Thanks for the help, all... I love forums - so amazing to have this sort of help when you're just getting started.
Hi Yannie,
Looking forward to see your results.
Such linear power supplies are simple in nature and should be tested like that: The input AC voltage is reduced by a transformer to a voltage level the regulator circuit can handle, the output voltage from the transformer secondary (AC) is rectified and stored on a storage capacitor(s), the voltage on the storage capacitor(s) is used as input to a regulator circuit and the regulator circuit reduces its input voltage to the output voltage you can expect.
When you test such a circuit, you basically follow that flow. It is very rare that a transformer, having a correct sine-wave level at the input, hasn't a more or less correct sine-wave output (secondary) voltage. So, we go straight to looking at the rectified voltage. This is what I suggested in my first posting.
What is the expected regulated output voltage from the board?
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Hi all,
Sorry about the delay - life got in the way of the project.
The regulator is the LD1284V (link)
I have made some changes to my testing setup based on recommendations above and from the seller of the kit. I am now using the VARIAC to power the transformer that will be used for the project (120vac in to dual 12vac out) and using one of the 12vac out to power the board (isolation so I don't blow up my scope - thanks!). I've tried measuring off the outputs and the ground to positive lead of C5 - both are only reading a couple of mv - I fear I've cooked something in my attempts to power the board... perhaps the LD1084?
The output voltage from the board should be 12VDC (will feed a DAC) while the other leg of the transformer feeds a 12VAC tube buffer (tube buffered DAC project).
I also tried with the resistor across the output leads (no change from above results).
Sorry about the delay - life got in the way of the project.
The regulator is the LD1284V (link)
I have made some changes to my testing setup based on recommendations above and from the seller of the kit. I am now using the VARIAC to power the transformer that will be used for the project (120vac in to dual 12vac out) and using one of the 12vac out to power the board (isolation so I don't blow up my scope - thanks!). I've tried measuring off the outputs and the ground to positive lead of C5 - both are only reading a couple of mv - I fear I've cooked something in my attempts to power the board... perhaps the LD1084?
The output voltage from the board should be 12VDC (will feed a DAC) while the other leg of the transformer feeds a 12VAC tube buffer (tube buffered DAC project).
I also tried with the resistor across the output leads (no change from above results).
OK - back to basics.
Disconnect the transformer from the regulator board. Put 120Vac on the primary terminals of the transformer. Connect the ground-clip of the oscilloscope probe to the end of one secondary winding and the probe-tip to the other end of that secondary winding. You are supposed to see a sine-wave with an amplitude close 35V peak-to-peak. Correct? Then, do the same for the other secondary winding and check that you also have 35V peak-to-peak on that winding.
Disconnect the transformer from the regulator board. Put 120Vac on the primary terminals of the transformer. Connect the ground-clip of the oscilloscope probe to the end of one secondary winding and the probe-tip to the other end of that secondary winding. You are supposed to see a sine-wave with an amplitude close 35V peak-to-peak. Correct? Then, do the same for the other secondary winding and check that you also have 35V peak-to-peak on that winding.
13.4vac rms and 19vac max with 120v input....
Did I do something stupid on the purchase of the power transformer?
1182P12 Hammond Manufacturing | Transformers | DigiKey
Perhaps because this is 50/60hz and I'm feeding it 60?
These are the specs on the main page at Digikey...
Voltage - Primary 117V
Voltage - Secondary (Full Load) Parallel 12V, Series 24V
Current - Output (Max) Parallel 10A, Series 5A
Did I do something stupid on the purchase of the power transformer?
1182P12 Hammond Manufacturing | Transformers | DigiKey
Perhaps because this is 50/60hz and I'm feeding it 60?
These are the specs on the main page at Digikey...
Voltage - Primary 117V
Voltage - Secondary (Full Load) Parallel 12V, Series 24V
Current - Output (Max) Parallel 10A, Series 5A
Nope! You have an entirely suitable transformer, albeit considerably stronger than needed to supply these current requirements. 50/60 Hz means just what you'd think: It has sufficient inductance and magnetic 'mass' to provide the indicated performance at either frequency.
But 'what does the scope trace show' is what I think we're asking. The Vac RMS measurements are somewhat reassuring, but requires that we *know* the equipment providing the measurement.
[Borrowing from FauxFrench, post 10:]
With the 'scope ground clip on one lead of one secondary, and the tip clipped on the other lead of that secondary, what does the waveform look like? And what does it measure peak-to-peak?
Enough unexpected test results and the only reasonable option becomes 'start with the basics'.
Cheers
But 'what does the scope trace show' is what I think we're asking. The Vac RMS measurements are somewhat reassuring, but requires that we *know* the equipment providing the measurement.
[Borrowing from FauxFrench, post 10:]
With the 'scope ground clip on one lead of one secondary, and the tip clipped on the other lead of that secondary, what does the waveform look like? And what does it measure peak-to-peak?
Enough unexpected test results and the only reasonable option becomes 'start with the basics'.
Cheers
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OK, that looks about right. That's with no load, isn't it -- nothing else connected to that secondary?
That's right, nothing else connected, just 120 off the VIRIAC and the leads on one of the secondary winding pairs.
OK. Now connect just the ground clip to one side of the bridge rectifier input to the regulator board, leaving both transformer secondary leads connected as before.
Then watch for any changes to the 'scope trace.
Then watch for any changes to the 'scope trace.
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Very good guidance by Rick.
As you can see, we now got back to a measurement that "makes sense" (a result as expected). This is what I call "back to basics". 37Vpp from a secondary winding on the transformer. The transformer is OK.
Then we start moving slowly forward in the signal path until we get to a measurement that does not "make sense".
As I understand Rick's guidance, the next measurement is with a transformer secondary winding (anyone of the two secondary windings)
connected to the power input terminals of the regulator board. At the same time we want to measure if the AC-voltage from the transformer winding remains looking about the same as before (not connected), in particular that the amplitude of the AC voltage remains at the same level. If there is a failure on the regulator board, pulling so much current from the transformer winding that the voltage (AC) is lowered considerably, operating the circuit like this may cause further damage.
So, turn OFF the 120Vac to the primary winding, connect the transformer secondary to the regulator board terminals, connect the scope-probe ground clip and probe tip to the same power input terminals and no load at the output of the regulator board. Then, watch the signal at the scope as you turn ON the 120Vac at the primary - if the sine-wave is now reduced importantly in amplitude or heavily distorted, the regulator board is loading the transformer too heavily and you have to switch the power OFF again and tell us. If the sine-wave remains about as before, post us a photo and it is time to do DC measurements on the regulator board.
Your last scope-photo is very good, just as we prefer them.
As you can see, we now got back to a measurement that "makes sense" (a result as expected). This is what I call "back to basics". 37Vpp from a secondary winding on the transformer. The transformer is OK.
Then we start moving slowly forward in the signal path until we get to a measurement that does not "make sense".
As I understand Rick's guidance, the next measurement is with a transformer secondary winding (anyone of the two secondary windings)
connected to the power input terminals of the regulator board. At the same time we want to measure if the AC-voltage from the transformer winding remains looking about the same as before (not connected), in particular that the amplitude of the AC voltage remains at the same level. If there is a failure on the regulator board, pulling so much current from the transformer winding that the voltage (AC) is lowered considerably, operating the circuit like this may cause further damage.
So, turn OFF the 120Vac to the primary winding, connect the transformer secondary to the regulator board terminals, connect the scope-probe ground clip and probe tip to the same power input terminals and no load at the output of the regulator board. Then, watch the signal at the scope as you turn ON the 120Vac at the primary - if the sine-wave is now reduced importantly in amplitude or heavily distorted, the regulator board is loading the transformer too heavily and you have to switch the power OFF again and tell us. If the sine-wave remains about as before, post us a photo and it is time to do DC measurements on the regulator board.
Your last scope-photo is very good, just as we prefer them.
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Thanks guys - this is great - learning as we go.
I'll owe you all a beer - or at least a photo of the finished product!
Here's the scope output with the regulator attached.
I'll owe you all a beer - or at least a photo of the finished product!
Here's the scope output with the regulator attached.
Also, based on the results from that test, I’m assuming we’re moving down the signal path. Feel free to give me a few points if that makes sense to try to get a few data points in one response.
Looks perfectly well. Now time for the DC-measurements.
No load for a start. OSCILLOSCOPE IN DC-MODE. If not (AC mode), you will tell us that there is no voltage. Probe ground-clip to output GND/"-" for the following four measurements. Probe-tip on:
1) C5"+"; the voltage here should be an almost straight horisontal line at around 17Vdc.
2) C6"+"; the voltage here should be an almost straight horisontal line at a voltage little less than on C5"+".
3) C7"+"; the voltage here should be an almost straight horisontal line at just below 11Vdc.
4) C8"+"; the voltage here should be an almost straight horisontal line at close to 12Vdc.
We are curious to see the results.😱
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