Mr Carlson's Lab patreon

A Device To Discharge High Voltage Capacitors Safely, Let's Design This.

🕑 Added 2018-02-02 03:11:28 +0000 UTC

Comments

Salvatore Marino

Mr Carlson I will like the file and schematic to build the capasitor discharge,video 37&38. My Email smarino51@hotmail.com Thank you

Richard

Our radar had a big stick with a wire to ground with some stickers in the cabinet on where to touch. Then someone was behind you with a large candy cane safety stick if things didn't go right.

LoSaYa

Great Work Thank You

Matt Stephanson

Entering the part # from Mr. C’s list into Mouser.ca, you get a bunch to choose from. The first in the list is this one, dimensions are on that page: https://www.mouser.ca/ProductDetail/Hammond-Manufacturing/1591ESBK?qs=%252Bn8HNu1qIodFbLJVEG%252B9tA%3D%3D

Cedric Sehas

HI Mr C. I love your videos. I'm finally building this circuit. What is the dimensions of the Hammond Box. Can't find a specific size size for that part no. Thanks.

Steve Simmonds

This could be modified to use an opto-isoloator or LDR and one transistor to drive a high-intensity single LED and a buzzer. This means you don't have to keep looking at the box or meter and can quickly go round every capacitor and just listen to the buzzer which will stop when the cap is discharged. You could also test the box before you use it by dabbing the probes across a 9V battery (both ways) and check you hear the buzzer.

Michael Clutton

Thank you

Mr Carlson's Lab

Hi Michael. Video 037 and video 038 deal with this topic.

Michael Clutton

I have been a Patreon, for a long time but have not really made use of the excellent information available. I would like to build the capacitor discharger, but the only information I can find is the first video and a parts list.

Bruce Dow

Mr Carlson, I'm glad to see you like Duracell[TM] too! :-)

Seth Burgin

My circuit is 100% correct but the schematic looks more like how the main 1K resistors will be screwed to a bit of heatsink I salvaged from an old Akai or Aiwa stereo's one channel's STK block(s) heat sink. I added a thermal cutout to open the circuit and illuminate a neon indicator if one of the resistors goes over 75 degrees C. It will not close again until it gets to 50 C, or 122, which could the be LESS than the ambient temperature where I live!

C.T.

Thank you Paul. I have an AS from Wentworth Institue back in

Mr Carlson's Lab

It's in the attachment under the description of this video: <a href="https://www.patreon.com/posts/parts-list-parts-21155037">https://www.patreon.com/posts/parts-list-parts-21155037</a>

C.T.

Does anyone have a part number for a sensitive L.E.D. for this circuit?

Escabusa Roy

Great device for discharging large capacitor and also clear explanation. Thanks sir Paul.

Mr Carlson's Lab

Hi Greg. The best place to post questions is in the community section, you will get immediate exposure there. Older posts will take a while for responses.

Greg Newberry

Anyone have a suggested brand for the test leads? Seems that the import models that I've looked at are not really up to par... :)

George Noyb

Re designing the schematic myself, I am not confident that I can tackle that yet. And to that end I think that Mr Carlson could do a better job in showing the progression of exercises that would lead to this exercise. I am willing to start over at step 1 if I only knew what it was. Regards.

Mr Carlson's Lab

Great! You're welcome David.

David Wiszczor

Completed my capacitor drain project last night, I am new to electronics so it took longer than I thought it would. Did mine on a project breadboard. Really look forward to using it. Passed the 9V battery test and had correct ohms reading 3,984 Kilo Ohms. Thanks for such a great project!

Mr Carlson's Lab

Hi David. The glue is : LePage Super Glue Liquid Pro.

David Wiszczor

Can you let us in on the name of the bonding agent you use?

Mr Carlson's Lab

The answers are one video up.

Helmut Heller

When are you going to publish your video about the answers on YT?

Mr Carlson's Lab

Care to explain?

John Proctor

posted to community. remove it or move it is that's not really the way to post exercise responses.

Dennis Cabell

Oh YES! I like this!. I wish I would have thought of this. Can I change my Answer :)

Neonuros

Regarding the two sets of probes, I'm thinking cut the probe tips off one set and the plugs off the other. This gives you a set of insulated plugs to connect to a multimeter to verify safe discharge... And probes on the other set are used to discharge the capacitor...

Mr Carlson's Lab

I would.

Mr Carlson's Lab

Got it, thanks!

Andreas Sidiropoulos

I put my schematic in the community section.

Bill Strider

The probes arrived today. I ordered 1000V 20A, and that's what the invoice says, but the probes themselves are clearly marked "10A". I guess I'll send these back and try again.

Mr Carlson's Lab

Thanks for your entry Matt.

Matt Hogstrom

Rushed this one in. My thought was to consider a circuit that had all probes in place and you could use any red / black pair. Bothers me that the other probes will see voltage, need to think about that a bit. A bit wonky, thoughts welcome. Tried to focus on redundancy where we could withstand a single failure of any component. <a href="https://scontent-atl3-1.xx.fbcdn.net/v/t31.0-8/27912690_521426284906188_3500769900914237391_o.png?oh=178ece805564b25178974ff4a646c7df&oe=5B0C8F0B" rel="nofollow noopener" target="_blank">https://scontent-atl3-1.xx.fbcdn.net/v/t31.0-8/27912690_521426284906188_3500769900914237391_o.png?oh=178ece805564b25178974ff4a646c7df&oe=5B0C8F0B</a>

Mr Carlson's Lab

Look forward to seeing it Matt.

Mr Carlson's Lab

Thanks for your entry Dennis.

Mr Carlson's Lab

Thanks for your entry Peter.

Peter Sage

In the interest of redundancy, Paul said this will have a lot of redundancy built in. I think 4K is an incredibly low impedance to place across a 100uF/450V capacitor, and resistors in series have no redundancy. My submission: (withdrawn after further thought; can't make the math work without putting the 4 power resistors in series)

Dennis Cabell

Here is my guess. Any 2 probes can be used for different resistances and any 2 used will provide some current to the LEDs. LEDs and 300 Ohm resistor positions could also be swapped. <a href="https://photos.app.goo.gl/1ygn9Dnmsw144QxU2" rel="nofollow noopener" target="_blank">https://photos.app.goo.gl/1ygn9Dnmsw144QxU2</a>

Smitty Nash

I was thinking that with four probes you'd be able to discharge a multi-cap can which is found in a lot of tube equipment. But he said "redundancy" which may mean two individual dischargers in a box in case one failed during a project. Another way of making it redundant might be to ensure bi-polar discharging thus the two LED/Zener diode pairs would tell you what you need to know regardless of the polarity of the cap. There are non-polorized caps (polypropylene for example) that you would want discharged too so polarity would have to be assumed to be unknown in order to get an indication. Will be interesting to see the answer when he's ready.

Matt Hogstrom

Been playing around with the components. What I'm contemplating is if I'm building the same circuit twice (the two sets of leads kind of throws me off; is one a backup for the other or are there two circuits). Zeners and LEDs make sense, kind of clever actually. I'll have my entry in tomorrow or so :)

Mr Carlson's Lab

Hi RB Evans, the answers will be included in the next video.

Mr Carlson's Lab

Hi Einar. The answers will be included in the next video.

Mr Carlson's Lab

Hi Albert. It's coming, just waiting to give everyone to get a fair chance to enter.

Albert G.

Hurry up! We are in suspense! How about a live webnar?

RBE

I couldn't get any further than guessing the 4, 50W resistors will be in series.

Einar Martin Meek

I was thinking maybe there are 2 sets of probes to drain capacitors of 2 different size groups? Big caps have a lot more energy stored than small caps and also terminals of small caps are not constructed for large current drains. So 1 set of probes for say caps under 500uF and 1 set for those over 500uF. The 2 sets of probes would go to 2 different drain resistors. The indicator circuit could be common.

Mr Carlson's Lab

Welcome Jeff, glad you're here!

Jeff hill

Im so Glad i became a Patreon looking forward to learning all i can from you Thank you

Mr Carlson's Lab

Thanks for your entry Mark.

Mark Frost

Here is my submission: <a href="https://photos.app.goo.gl/ofsvoPS5yLLJ3i6l2" rel="nofollow noopener" target="_blank">https://photos.app.goo.gl/ofsvoPS5yLLJ3i6l2</a>

Mr Carlson's Lab

I look forward to your entry Jemima.

Jemima Khan

:D I will try to take on this challenge!!

Mr Carlson's Lab

Thanks for your entry Xeroeffect.

Mr Carlson's Lab

Thanks for your entry Rob.

Xeroeffect

Hi guys. Ive also decided to take a stab in the dark and share my design with you. Hi Paul and thank you for your insight. :) <a href="https://drive.google.com/open?id=0Bz92zSjw0aAFWFRmaDdvd2lndXl4LUJwQ0E5UWg5SUhZZjA0" rel="nofollow noopener" target="_blank">https://drive.google.com/open?id=0Bz92zSjw0aAFWFRmaDdvd2lndXl4LUJwQ0E5UWg5SUhZZjA0</a>

Bill Strider

The one thing that has me stumped is why there are two 300-ohm resistors. Maybe this is the answer: <a href="https://www.dropbox.com/s/gptqj799lndelab/Discharge2.png?dl=0" rel="nofollow noopener" target="_blank">https://www.dropbox.com/s/gptqj799lndelab/Discharge2.png?dl=0</a>

Rob Clark

Here goes nothing: <a href="https://goo.gl/Z75Bbu" rel="nofollow noopener" target="_blank">https://goo.gl/Z75Bbu</a> My idea is that two probes are used at a time in a series of three steps. The first step discharges the bulk of the stored energy. Steps two and three complete the job. The order is important unless you want to see a pair of LEDs go into low-Earth orbit.

Bill Strider

This is what I came up with. I had no idea what to do with the second set of probes, so I ignored them. I figure the metal plate is there to provide a path to ground if one of those big resistors fails (or if there's a voltage high enough to cause an arc.) I believe the LEDs (one or the other) will light while the capacitor is discharging. The sensitivity to low voltage is important so the LED doesn't go dark prematurely. <a href="https://www.dropbox.com/s/a57x8lok97llftp/Discharge.png?dl=0" rel="nofollow noopener" target="_blank">https://www.dropbox.com/s/a57x8lok97llftp/Discharge.png?dl=0</a>

Bob Snyder

Additionally perhaps the second set of probes could be connected where the 68k resistors are for when lower voltages are on the circuit.

Bob Snyder

I'm sure this is not right but what I am really interested in is why they aren't. If I get some time today I might breadboard this and probe around it with some low voltage. If someone could tell me why this would/would not work, that'd be awesome. I drew two options for the diode portions. Both options are using the 1K resistor network's voltage divider to lower the voltage seen in the diode area. Then I was thinking of an LED being lit depending on how the cap was connected. <a href="https://photos.app.goo.gl/HYzXXmkg3IoxMgT92" rel="nofollow noopener" target="_blank">https://photos.app.goo.gl/HYzXXmkg3IoxMgT92</a>

Mr Carlson's Lab

Thanks for your entry Tinkertubes.

Mr Carlson's Lab

You're Welcome James!

Robert Valdimarsson

For the power problem: keep in mind, that the maximum power of a fully charged cap is only there for the first RC-time constant and decreases rather quickly from there. i frequently see people discharging caps with a 10ohm/20W concrete resistor, which they hold in their hand and from all the safety issues i can see there, heat seems to be the least of their problems. And for the second set of probes: i think something is connected to that heatsink somehow Oo because the radiators of the resistors are actually insulated. it could be a pure safety measure to isolate the heatsink, but he kinda stressed the fact a bit too much for that :D

Rob Clark

I'm scratching my head, too, James. Being a two-handed person myself, it seems that only two probes can be used at a time unless my assistant Beaker holds the other two. That never seems to end well. The Zener diodes have a maximum reverse voltage which must be considered. Also, putting resistors in parallel seems like a P=I2R problem as well if my math is correct. I have an idea that the second set of probes is for the coup-de-grace after the LED forward voltage is reached, but I can't think of a foolproof way to do it. And Beaker is very clumsy...

Leland Clayton

My guess the Zener diodes will limit the voltage going into the discharger and from there it will just go into the resistors in a parallel configuration. Watch I will probably be totally wrong.

James A Wilson

Hi Mr Carlson, loving the patreon channel, making me scratch my head in a very good way!! This cap discharger is already a must for me. Thanks again J

Ysjoelfir

I would go with this approach, at least that is the way I built my own discharging device and it works a treat. <a href="http://img.tinkertubes.de/cap%20discharge.PNG" rel="nofollow noopener" target="_blank">http://img.tinkertubes.de/cap%20discharge.PNG</a> I have to admit that I am a bit irritated about the second set of test leads. Just for spares since the tips degrade rather fast? It can't be a connection to some external meter, that could potentially be dangerous if I don't overlook something. I also thought about this (not very practical) idea which could potentially be dangerous and could damage the resistors if you attempt to discharge several caps which are charged to 800v or more in a row since only 100W of power is there in the worst case: <a href="http://img.tinkertubes.de/cap%20discharge%202.PNG" rel="nofollow noopener" target="_blank">http://img.tinkertubes.de/cap%20discharge%202.PNG</a> You would also make sure that you hold the chassis clip connected first using your third hand and you should flip the leads after one led stops glowing. So not really the best idea, but hey, it uses one and a half sets of test leads! :-P

Robert Valdimarsson

It seems everybody else has the 68k resistors in a series parallel arangement. my first draft had this too, but 68k seems to be too high to allow for the leds to light up at low-ish voltages and would cause the zeners to drop out even at still dangerous voltages. but i might have to do the full maths on that and it depends on the I(min) of the zener used.

Robert Valdimarsson

and my try. not sure if the 300 ohm resistors are in series in the common cathode (but the maths seem to work out this way) and i could not find a place for the second set of probes :D <a href="https://www.dropbox.com/s/bivvu46wcbkx3c0/IMG_20180202_220830.jpg?dl=0" rel="nofollow noopener" target="_blank">https://www.dropbox.com/s/bivvu46wcbkx3c0/IMG_20180202_220830.jpg?dl=0</a>

Mr Carlson's Lab

Thanks for your entry Yannick.

Yannick Turcotte

This is my try Paul. <a href="https://1drv.ms/i/s!AnKLPDy3pII_gnW9j2tvykgB4HqR" rel="nofollow noopener" target="_blank">https://1drv.ms/i/s!AnKLPDy3pII_gnW9j2tvykgB4HqR</a>

Mr Carlson's Lab

Thanks for your entry Axel.

Axel

Many thanks for this idea of sharing ideas. Maybe a circuit dealing with half V max for the leds : <a href="https://imgur.com/gallery/83Y6k" rel="nofollow noopener" target="_blank">https://imgur.com/gallery/83Y6k</a>

Mr Carlson's Lab

Thank You for your entry Ralf!

Reb Elba

Great Idea Paul, many thanks! I really like this little challenge, regardless if my attempt is a shoot in the oven in the end ;) I've done a quick simulation with your given components and this was the result with around 5mA at each LED with 400V charged cap. <a href="https://rebelba42.lima-city.de/img/media/cdp/cdp-circuit.png" rel="nofollow noopener" target="_blank">https://rebelba42.lima-city.de/img/media/cdp/cdp-circuit.png</a> After looking other comments, I agree with Helmut and have also no idea about the purpose of the second pair of probes. Can't wait so see part II :D

Mr Carlson's Lab

Thanks for your entry Helmut.

Helmut Heller

Hi Paul! Great idea to involve your followers -- big fun! :-) Given your parts list, I would do it like this: <a href="http://heller.no-ip.org/~heller/test/IMG_8752.jpg" rel="nofollow noopener" target="_blank">http://heller.no-ip.org/~heller/test/IMG_8752.jpg</a> Clearly, the 1k power resistors will bleed the capacitor. Putting them in series will limit the current to 200mA if the cap is charged to 800V (I don't think higher voltages are common). The 68k are the main LED resistors -- you already hinted at that with your body resistance. So the LED will go dim at around 9V, which is no longer harmful. From 800V we get a maximum of 11 mA, which is just fine for the LEDs. However, at 800V and 11mA you have to dissipate 10W in these resistors, so you use 4 of them (two in series, double the resistance, then parallel the strings to bring it back to 68k) since each only has 2W; this also increases the voltage rating of the 4 resistor sub-circuit. You could also connect them in the middle. And using 4 Rs will make your circuit error tolerant: if any one resistor fails, it will still work. Quite important for safety reasons. To further protect the LEDs you use the Zener, limiting the voltage to 5.6V and from there you use the 300 Ohms to limit the current through the LEDs. Since polarity might be unknown, you use two LEDs, one for each polarity. You could parallel the LEDs directly and spare one 300 Ohms resistor. I only don't know what you need that second set of probes for...

stephen hulten

For cheap probes that meet the requirements (20amp 1000V), check on ebay for Victor brand multimeter probes. Mostly shipped from china for about $6.

Mr Carlson's Lab

Thanks for your entry John.

Mr Carlson's Lab

OK, one more hint... It's only one tool. I will answer all entries at the launch of the next video.

John

Here's my guess. LEDs light while capacitor still has sufficient charge. <a href="https://imgur.com/a/zKGGA" rel="nofollow noopener" target="_blank">https://imgur.com/a/zKGGA</a>

Rod Smallwood

I see two discharge tools. Same in both cases. Red probe to top of four resistor string, String the zener, led and 300 ohm across bottom resistor. Black probe to bottom resistor.