You are very lucky that you didn't blow up your scope or harmed yourself. So many things could go wrong in this video. First of all, that Auto Variable Transformer, or Autotransformer or also called Variac, which in fact is a brand name for a autotransformer has only 1 coil. This means that the output is NOT isolated from mains. There are Autotransformers / Variacs with isolated outputs, but these are way more expensive and harder to find. In this video, you are using a portable scope, that's fine, because if used a regular scope which has the negative of the BNC connected to earth, you could in best case scenario trip your RCD if you connect the ground clip of your scope probe to the neutral, and in worst case scenario, when you clip the ground clip of your scope probe to the live, you will blow up your scope probe, and the front end of your scope itself, and maybe harm yourself with burn marks if the negative ground wire of your scope probe blows up. Also, with a regular scope, when connected to a bridge rectifier, that is referenced to mains ground, you will bypass 1 diode, and you still get a 100Hz / 120Hz bumps pulsating DC, no mather how much capacitance you add to the bridge rectifiers output. The reason that you are lucky in your setup, is that none of your devices has a grounded negative connection, or hell breaks loose. For best safety, you hook up that Vevor Autotransformer to a isolation transformer, that way you are no longer mains referenced and can't blow up things, as long as you don't connect any device that has negative connected to ground. And with almost 99% of portable scopes, if you connect them via USB to a desktop, you are grounding your scope. Same if the charger has a ground pin, the ground of a charger is in 99% connected to the negative part of the DC output jack, so you are grounding your portable scope that way, which can cause the above situtations. Grtz
Thank you Bjorn, and I love your comment - information like this is very very good to know. The reason I felt comfortable using this scope is because it is isolated from ground, but you are extremely right about your thoughts. I would hate to use a plug-in scope as that would definitely have ruined the scope and probably would have shocked me as well :). While editing the video, I did realize that the reason the wave was not completely smoothing out was (like you said), not going to go completely away no matter how many capacitors I use, but we can get the wave as smooth as possible using at least 3 capacitors is parallel. This video was a fun project, but you are right also that whenever we are dealing with such currents and AC, we need to be very careful not to overlook grounds. I would also love to use a isolated transformer for the Variac, but they are very very expensive and I simply can't afford such a device, as I have looked into those and can't see being able to afford one of those, so just have to think a little outside the box on using a scope. I am learning as I go, so getting incredible information from people like you, is very helpful. Thanks again for your insight and suggestions - they are very much appreciated. 👍👍
@@Outside-In. No problem at all, i'm also not a engineer or any kinds, but a electronic hobbyist with a reasonable knowledge that i like to share where i can. Arround 4 years ago,when i bought my first bench scope second hand from E..y and did some reading prior before i bought it, i found some articles on forums regarding doing mains referenced measurings. The old skool guys told proud that they used socalled "cheater plugs" for decades, (which i don't recommend), these are adapterplugs that interupts the grouding pin to the scope. So they used there scopes without grounding connect. And yes, you are kind on the "safe" sight, and won't blow up your scope or scope probe when connecting to mains, but lifting / not using a grounding on a bench scope give a lot of other problems. In almost any bench scope there is a netfilter on the mains input, this filter contains socalled safety X and Y capacitors (blue colored useally), there is a X capacitor between live and neutral, and a Y capacitor between live and ground, and a Y capacitor between neutral and ground. These capacitors causes some very low current flowing between mains and ground, the amount of current depends on the age of netfilters. In the very old netfilters, this "ground" current can be a few mA's, now these days this current is lower due lower capacity of these caps. But the thing is, when you use a cheater plug for a bench scope, this netfilter can't leak to ground, and arround 50% of the mains voltage (arround 60 to 120V, depending on the country you live) will be present on the outer ring of the BNC connectors of the scope. This 60 to 120V is at very low current, and can only give you a tingle,but it can cause damage to sensitive circuits connected to the scope. Especially circuits with Mosfets, which are very sensitive. A second problem raise, is that a scope probe uses a "single point" measuring, where the signal on the central pin is in reference to the 0V grounding. But because the grounding of the scope carry arround 50% of the mains voltage, your 0V isn't 0V in practice. On the scope itself it says 0V, because the scope doesn't know that the grounding is not connected to the ground of the mains grid. So your readings can have a offset because that 50% of the mains is riding on top of your real voltage you are measuring. And third problem is that a scope without a decent grounding connected, will pick up all kinds of interference which can have influence if you are measuring very low voltage readings. So ideal is to use a isolation transformer to power your device under test, and connect the bench scope to a mains outlet WITH ground connect. Because the output of a isolation transformer is not ground referenced, you can connect the ground clip of the scope probe to it without doing damage or hurt yourself. A isolation transformer can be very expensive, but you also hook up 2 normal transformers like 120V to 12V back to back. So the first transformers output is connected to the output of the second transformer, and the normal input of the second transformer becomes now your isolated output. So for 120V mains voltage, you go from 120V to 12V, and back from 12V to 120V (in theory). I say in theory, because in practice you will loose a few volts in the transformation. This 120V to 12V is a example, you can even choose for 2x transformers with each 120V to 24V. This can be a cheaper solution for low wattage repairs and testing. Grtz
@@BjornV78 Great information again. The way that I would like to do it because of not having the money to buy an isolation transformer, would be to just use a power inverter to power the scope, and that way there will be no connection to mains ground of your electric company. I am sure if that is wrong, you will say so :). I have done loads of research myself on scopes and how to use them, and I have found that a lot of people are just finding ways to connect their scopes to a battery, or a 120v scope can still be used on battery by using a inverter, and since I have an inverter, that is how I would use a mains scope - if I can ever afford one that is.. Great information Bjorn, and thanks so much for sharing your knowledge with us - 👍👍
I use a Auto Variable Transformer along with a full bridge rectifier, and add different capacitors to find out if we can make a DC power supply. Thank you Joe Jarrell for the inspiration for creating this video. If you like this type of video, please let me know in the comments about a subject you would like to discuss and I will do my best to create a video on that subject, or if you have a video idea for a DIY project, A review of a product or anything else, I will be happy to create that content as well. If you would like to help me keep this channel going, please follow link below. Anything you could do to help would be much appreciated, and enable me to do more to help you and the community. paypal.com/paypalme/StevenJarrell?country.x=US&locale.x=en_US Thanks for stopping by, and remember - find someone who needs to laugh, needs to smile, needs to cry, or just simply needs a friend - and make it happen ;). --------------------------------------------------------------------------------------- Items Used: * VEVOR 2000VA Auto Variable Voltage Transformer, 15.3 Amp, 110V Input 0-130V Output: www.amazon.com/gp/product/B0CZ3TV6ZR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8
You are very lucky that you didn't blow up your scope or harmed yourself.
So many things could go wrong in this video.
First of all, that Auto Variable Transformer, or Autotransformer or also called Variac, which in fact is a brand name for a autotransformer has only 1 coil.
This means that the output is NOT isolated from mains. There are Autotransformers / Variacs with isolated outputs, but these are way more expensive and harder to find.
In this video, you are using a portable scope, that's fine, because if used a regular scope which has the negative of the BNC connected to earth,
you could in best case scenario trip your RCD if you connect the ground clip of your scope probe to the neutral, and in worst case scenario, when you clip the ground clip of your scope probe to the live, you will blow up your scope probe, and the front end of your scope itself, and maybe harm yourself with burn marks if the negative ground wire of your scope probe blows up.
Also, with a regular scope, when connected to a bridge rectifier, that is referenced to mains ground, you will bypass 1 diode, and you still get a 100Hz / 120Hz bumps pulsating DC, no mather how much capacitance you add to the bridge rectifiers output.
The reason that you are lucky in your setup, is that none of your devices has a grounded negative connection, or hell breaks loose.
For best safety, you hook up that Vevor Autotransformer to a isolation transformer, that way you are no longer mains referenced and can't blow up things,
as long as you don't connect any device that has negative connected to ground.
And with almost 99% of portable scopes, if you connect them via USB to a desktop, you are grounding your scope.
Same if the charger has a ground pin, the ground of a charger is in 99% connected to the negative part of the DC output jack, so you are grounding your portable scope that way,
which can cause the above situtations. Grtz
Thank you Bjorn, and I love your comment - information like this is very very good to know. The reason I felt comfortable using this scope is because it is isolated from ground, but you are extremely right about your thoughts. I would hate to use a plug-in scope as that would definitely have ruined the scope and probably would have shocked me as well :).
While editing the video, I did realize that the reason the wave was not completely smoothing out was (like you said), not going to go completely away no matter how many capacitors I use, but we can get the wave as smooth as possible using at least 3 capacitors is parallel.
This video was a fun project, but you are right also that whenever we are dealing with such currents and AC, we need to be very careful not to overlook grounds.
I would also love to use a isolated transformer for the Variac, but they are very very expensive and I simply can't afford such a device, as I have looked into those and can't see being able to afford one of those, so just have to think a little outside the box on using a scope.
I am learning as I go, so getting incredible information from people like you, is very helpful.
Thanks again for your insight and suggestions - they are very much appreciated. 👍👍
@@Outside-In. No problem at all, i'm also not a engineer or any kinds, but a electronic hobbyist with a reasonable knowledge that i like to share where i can.
Arround 4 years ago,when i bought my first bench scope second hand from E..y and did some reading prior before i bought it, i found some articles on forums regarding doing mains referenced measurings. The old skool guys told proud that they used socalled "cheater plugs" for decades, (which i don't recommend), these are adapterplugs that interupts the grouding pin to the scope. So they used there scopes without grounding connect. And yes, you are kind on the "safe" sight, and won't blow up your scope or scope probe when connecting to mains, but lifting / not using a grounding on a bench scope give a lot of other problems.
In almost any bench scope there is a netfilter on the mains input, this filter contains socalled safety X and Y capacitors (blue colored useally), there is a X capacitor between live and neutral, and a Y capacitor between live and ground, and a Y capacitor between neutral and ground. These capacitors causes some very low current flowing between mains and ground, the amount of current depends on the age of netfilters. In the very old netfilters, this "ground" current can be a few mA's, now these days this current is lower due lower capacity of these caps. But the thing is, when you use a cheater plug for a bench scope, this netfilter can't leak to ground, and arround 50% of the mains voltage (arround 60 to 120V, depending on the country you live) will be present on the outer ring of the BNC connectors of the scope. This 60 to 120V is at very low current, and can only give you a tingle,but it can cause damage to sensitive circuits connected to the scope. Especially circuits with Mosfets, which are very sensitive.
A second problem raise, is that a scope probe uses a "single point" measuring, where the signal on the central pin is in reference to the 0V grounding.
But because the grounding of the scope carry arround 50% of the mains voltage, your 0V isn't 0V in practice. On the scope itself it says 0V, because the scope doesn't know that the grounding is not connected to the ground of the mains grid. So your readings can have a offset because that 50% of the mains is riding on top of your real voltage you are measuring.
And third problem is that a scope without a decent grounding connected, will pick up all kinds of interference which can have influence if you are measuring very low voltage readings. So ideal is to use a isolation transformer to power your device under test, and connect the bench scope to a mains outlet WITH ground connect. Because the output of a isolation transformer is not ground referenced, you can connect the ground clip of the scope probe to it without doing damage or hurt yourself. A isolation transformer can be very expensive, but you also hook up 2 normal transformers like 120V to 12V back to back.
So the first transformers output is connected to the output of the second transformer, and the normal input of the second transformer becomes now your isolated output. So for 120V mains voltage, you go from 120V to 12V, and back from 12V to 120V (in theory). I say in theory, because in practice you will loose a few volts in the transformation. This 120V to 12V is a example, you can even choose for 2x transformers with each 120V to 24V.
This can be a cheaper solution for low wattage repairs and testing. Grtz
@@BjornV78 Great information again. The way that I would like to do it because of not having the money to buy an isolation transformer, would be to just use a power inverter to power the scope, and that way there will be no connection to mains ground of your electric company. I am sure if that is wrong, you will say so :). I have done loads of research myself on scopes and how to use them, and I have found that a lot of people are just finding ways to connect their scopes to a battery, or a 120v scope can still be used on battery by using a inverter, and since I have an inverter, that is how I would use a mains scope - if I can ever afford one that is..
Great information Bjorn, and thanks so much for sharing your knowledge with us - 👍👍
Great video!
Thanks, I did have a lot of fun with this one. Hope to get to do more like this. 👍
Interesting and informational video I thank it is cool that I inspired you to do this
Thank you Joe. This was the most I ever worked on one video :). The video coming up is not going to take as long to do... 👍
I use a Auto Variable Transformer along with a full bridge rectifier, and add different capacitors to find out if we can make a DC power supply. Thank you Joe Jarrell for the inspiration for creating this video.
If you like this type of video, please let me know in the comments about a subject you would like to discuss and I will do my best to create a video on that subject, or if you have a video idea for a DIY project, A review of a product or anything else, I will be happy to create that content as well.
If you would like to help me keep this channel going, please follow link below. Anything you could do to help would be much appreciated, and enable me to do more to help you and the community.
paypal.com/paypalme/StevenJarrell?country.x=US&locale.x=en_US
Thanks for stopping by, and remember - find someone who needs to laugh, needs to smile, needs to cry, or just simply needs a friend - and make it happen ;).
---------------------------------------------------------------------------------------
Items Used:
* VEVOR 2000VA Auto Variable Voltage Transformer, 15.3 Amp, 110V Input 0-130V Output:
www.amazon.com/gp/product/B0CZ3TV6ZR/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8
* Baomain 100A Amp 1200V Volt Diode Bridge Rectifier:
www.amazon.com/gp/product/B008LTIMX4/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
* 10 Pieces 50V 4700UF Plug-in Aluminum Electrolytic Capacitor:
www.amazon.com/Pieces-4700UF-Aluminum-Electrolytic-Capacitor/dp/B0CFXJP49G/ref=sr_1_8?sr=8-8
* 4700uF 63V 22x40mm Electrolytic Capacitor (Pack of 5):
www.amazon.com/ALLECIN-Electrolytic-Capacitor-0-87x1-57in-Capacitors/dp/B0CMQ9XVCS/ref=sr_1_4?sr=8-4