A Device To Discharge High Voltage Capacitors Safely, Let's Design This.
Added 2018-02-02 03:11:28 +0000 UTCIn this video, we will begin to design a universal device to discharge capacitors safely. A very beneficial device when working on switch mode power supplies, vacuum tube equipment, and so on..... A description and parts list is laid out to get us started.
This is video #37, include this when requesting attachments.
Patreon NEW LIST of Videos: https://www.patreon.com/posts/8239565
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Parts list is attached below:
Comments
Mr Carlson I will like the file and schematic to build the capasitor discharge,video 37&38. My Email smarino51@hotmail.com Thank you
Salvatore Marino
2025-04-15 14:55:14 +0000 UTCOur 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.
Richard
2023-03-15 12:14:12 +0000 UTCGreat Work Thank You
LoSaYa
2022-10-18 21:37:20 +0000 UTCEntering 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
Matt Stephanson
2022-10-02 17:39:59 +0000 UTCHI 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.
Cedric Sehas
2020-08-24 17:10:19 +0000 UTCThis 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.
Steve Simmonds
2019-09-14 08:15:16 +0000 UTCThank you
Michael Clutton
2019-06-04 18:12:24 +0000 UTCHi Michael. Video 037 and video 038 deal with this topic.
Mr Carlson's Lab
2019-06-04 17:18:23 +0000 UTCI 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.
Michael Clutton
2019-06-04 14:33:03 +0000 UTCMr Carlson, I'm glad to see you like Duracell[TM] too! :-)
Bruce Dow
2019-05-17 17:52:29 +0000 UTCMy 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!
Seth Burgin
2018-12-23 13:00:25 +0000 UTCThank you Paul. I have an AS from Wentworth Institue back in
C.T.
2018-11-02 01:52:35 +0000 UTCIt'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>
Mr Carlson's Lab
2018-11-01 18:31:37 +0000 UTCDoes anyone have a part number for a sensitive L.E.D. for this circuit?
C.T.
2018-10-29 18:37:43 +0000 UTCGreat device for discharging large capacitor and also clear explanation. Thanks sir Paul.
Escabusa Roy
2018-07-01 09:40:05 +0000 UTCHi 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.
Mr Carlson's Lab
2018-06-18 22:22:12 +0000 UTCAnyone have a suggested brand for the test leads? Seems that the import models that I've looked at are not really up to par... :)
Greg Newberry
2018-06-18 20:17:57 +0000 UTCRe 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.
George Noyb
2018-04-25 15:30:36 +0000 UTCGreat! You're welcome David.
Mr Carlson's Lab
2018-04-23 17:25:32 +0000 UTCCompleted 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!
David Wiszczor
2018-04-23 17:13:46 +0000 UTCHi David. The glue is : LePage Super Glue Liquid Pro.
Mr Carlson's Lab
2018-03-10 21:38:06 +0000 UTCCan you let us in on the name of the bonding agent you use?
David Wiszczor
2018-03-10 13:20:34 +0000 UTCThe answers are one video up.
Mr Carlson's Lab
2018-03-04 11:13:15 +0000 UTCWhen are you going to publish your video about the answers on YT?
Helmut Heller
2018-03-04 10:37:51 +0000 UTCCare to explain?
Mr Carlson's Lab
2018-02-15 23:44:48 +0000 UTCposted to community. remove it or move it is that's not really the way to post exercise responses.
John Proctor
2018-02-15 18:27:46 +0000 UTCOh YES! I like this!. I wish I would have thought of this. Can I change my Answer :)
Dennis Cabell
2018-02-14 14:15:11 +0000 UTCRegarding 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...
Neonuros
2018-02-14 07:53:47 +0000 UTCI would.
Mr Carlson's Lab
2018-02-14 04:51:25 +0000 UTCGot it, thanks!
Mr Carlson's Lab
2018-02-14 04:50:49 +0000 UTCI put my schematic in the community section.
Andreas Sidiropoulos
2018-02-13 07:46:12 +0000 UTCThe 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.
Bill Strider
2018-02-13 01:06:10 +0000 UTCThanks for your entry Matt.
Mr Carlson's Lab
2018-02-12 03:53:49 +0000 UTCRushed 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>
Matt Hogstrom
2018-02-12 02:23:34 +0000 UTCLook forward to seeing it Matt.
Mr Carlson's Lab
2018-02-12 00:54:14 +0000 UTCThanks for your entry Dennis.
Mr Carlson's Lab
2018-02-12 00:49:49 +0000 UTCThanks for your entry Peter.
Mr Carlson's Lab
2018-02-12 00:49:22 +0000 UTCIn 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)
Peter Sage
2018-02-11 21:41:06 +0000 UTCHere 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>
Dennis Cabell
2018-02-11 19:12:55 +0000 UTCI 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.
Smitty Nash
2018-02-11 15:43:29 +0000 UTCBeen 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 :)
Matt Hogstrom
2018-02-11 01:51:58 +0000 UTCHi RB Evans, the answers will be included in the next video.
Mr Carlson's Lab
2018-02-10 19:55:43 +0000 UTCHi Einar. The answers will be included in the next video.
Mr Carlson's Lab
2018-02-10 19:54:43 +0000 UTCHi Albert. It's coming, just waiting to give everyone to get a fair chance to enter.
Mr Carlson's Lab
2018-02-10 19:53:34 +0000 UTCHurry up! We are in suspense! How about a live webnar?
Albert G.
2018-02-10 15:09:30 +0000 UTCI couldn't get any further than guessing the 4, 50W resistors will be in series.
RBE
2018-02-10 01:31:00 +0000 UTCI 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.
Einar Martin Meek
2018-02-09 15:45:30 +0000 UTCWelcome Jeff, glad you're here!
Mr Carlson's Lab
2018-02-09 08:06:57 +0000 UTCIm so Glad i became a Patreon looking forward to learning all i can from you Thank you
Jeff hill
2018-02-09 04:20:25 +0000 UTCThanks for your entry Mark.
Mr Carlson's Lab
2018-02-06 23:29:32 +0000 UTCHere is my submission: <a href="https://photos.app.goo.gl/ofsvoPS5yLLJ3i6l2" rel="nofollow noopener" target="_blank">https://photos.app.goo.gl/ofsvoPS5yLLJ3i6l2</a>
Mark Frost
2018-02-06 22:59:19 +0000 UTCI look forward to your entry Jemima.
Mr Carlson's Lab
2018-02-06 18:29:59 +0000 UTC:D I will try to take on this challenge!!
Jemima Khan
2018-02-06 04:48:27 +0000 UTCThanks for your entry Xeroeffect.
Mr Carlson's Lab
2018-02-04 11:59:45 +0000 UTCThanks for your entry Rob.
Mr Carlson's Lab
2018-02-04 11:59:01 +0000 UTCHi 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>
Xeroeffect
2018-02-04 06:49:09 +0000 UTCThe 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>
Bill Strider
2018-02-04 04:58:52 +0000 UTCHere 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.
Rob Clark
2018-02-04 04:11:18 +0000 UTCThis 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>
Bill Strider
2018-02-04 03:56:17 +0000 UTCAdditionally perhaps the second set of probes could be connected where the 68k resistors are for when lower voltages are on the circuit.
Bob Snyder
2018-02-03 17:08:37 +0000 UTCI'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>
Bob Snyder
2018-02-03 15:22:58 +0000 UTCThanks for your entry Tinkertubes.
Mr Carlson's Lab
2018-02-03 14:13:11 +0000 UTCYou're Welcome James!
Mr Carlson's Lab
2018-02-03 13:47:06 +0000 UTCFor 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
Robert Valdimarsson
2018-02-03 10:00:52 +0000 UTCI'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...
Rob Clark
2018-02-03 02:59:23 +0000 UTCMy 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.
Leland Clayton
2018-02-03 02:59:05 +0000 UTCHi 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
James A Wilson
2018-02-03 00:26:58 +0000 UTCI 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
Ysjoelfir
2018-02-03 00:12:38 +0000 UTCIt 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
2018-02-02 22:03:24 +0000 UTCand 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>
Robert Valdimarsson
2018-02-02 21:17:25 +0000 UTCThanks for your entry Yannick.
Mr Carlson's Lab
2018-02-02 15:26:12 +0000 UTCThis 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>
Yannick Turcotte
2018-02-02 14:52:54 +0000 UTCThanks for your entry Axel.
Mr Carlson's Lab
2018-02-02 13:23:58 +0000 UTCMany 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>
Axel
2018-02-02 12:59:06 +0000 UTCThank You for your entry Ralf!
Mr Carlson's Lab
2018-02-02 12:01:51 +0000 UTCGreat 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
Reb Elba
2018-02-02 11:41:25 +0000 UTCThanks for your entry Helmut.
Mr Carlson's Lab
2018-02-02 06:15:09 +0000 UTCHi 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...
Helmut Heller
2018-02-02 06:04:53 +0000 UTCFor cheap probes that meet the requirements (20amp 1000V), check on ebay for Victor brand multimeter probes. Mostly shipped from china for about $6.
stephen hulten
2018-02-02 05:19:54 +0000 UTCThanks for your entry John.
Mr Carlson's Lab
2018-02-02 05:00:58 +0000 UTCOK, one more hint... It's only one tool. I will answer all entries at the launch of the next video.
Mr Carlson's Lab
2018-02-02 04:57:06 +0000 UTCHere'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>
John
2018-02-02 04:56:26 +0000 UTCI 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.
Rod Smallwood
2018-02-02 04:52:13 +0000 UTC
