Please help with switch selection - Page 1
Forum section: electronics / beginners

author: shanezampire
author_rank: Contributor
timestamp: June 16, 2019, 06:07:32 pm
content: I have been searching for 2 days straight for a switch. I have learned a lot about switches so it wasn't a total waste but I can NOT find what I am looking for. I just need a simple, small, cheap, panel mount rotary switch. Would like to get it from ebay. I just don't know what the type name or what it would be labeled as so I can search for it proper. I need a 4 or 5 position rotary switch. One where I can connect 110/120v to terminal. When I switch it to (we will call it position 1) it will send the power to terminal (1) .... When I switch it to position 2 - it will send power to terminal (1) and (2) ... When I switch it to position 3 - it will send power to terminal (1) and (2) and (3) ... When I switch it to position 4 - it will send power to terminal (1) and (2) and (3) and (4)In my mind, I would think I am looking for a switch with 5 terminals. One to hook up the line in, and 4 other terminals to send the power out. Simple! But seems every switch I find, as you turn the switch, it picks only one terminal to make connection to. Its doesn't keep adding to them.I need it for a capacitive battery charger. I am using 4 different size capacitors of different sizes. I would like to be able to power them in a parallel series depending on the size battery I need to charge.I know I could just use 4 toggle switches but seems one rotary switch would be much simpler and take us less room.Thanks in advance for any help!

author: Zero999
author_rank: Super Contributor
timestamp: June 16, 2019, 08:35:16 pm
content: I hven't seen such a switch before. If it's DC and a small voltage drop is acceptable, you could use a single pole quadruple through rotary switch with ORing diodes. Failing that, you need a 4P4T configuration.

author: Ian.M
author_rank: Super Contributor
timestamp: June 16, 2019, 09:40:26 pm
content: A capacitive dropper power supply is unsafe for any application where there is even a remote chance of the user (or anyone else) coming into contact with the load circuit. Don't use one for a battery charger unless it is solely for the internal battery of a sealed double insulated or grounded case appliance with no external connections apart from its mains supply, or unless your battery compartment has a tamperproof lid interlock switch that cuts both poles of the mains supply before it can be opened.Unlike a toggle switch, most rotary switches don't have a sharp 'snap' action (exception: ones that use cams to operate heavy duty microswitches). If you use a wafer rotary switch to switch capacitors in parallel with power applied, the contacts will burn as they engage. Even toggle switches (or rotary cam operated switches) would be unreliable for this application without a resistor in series with each capacitor to limit the surge current.TLDR: You are building a deathtrap. Stop and seek advice before it kills someone.It reminds me of stories I heard from my mentors when I was a youngster, of the bad old days when people would charge the Lead Acid LT accumulator of their tube radio by placing it in series with an electric heater run off their DC mains supply!

author: Doctorandus_P
author_rank: Super Contributor
timestamp: June 16, 2019, 09:54:08 pm
content: There are industrial type rotary switches that can switch 230Vac and are stackable, but these are quite big.Rotary switches also were very common on those old analog scopes, but those were all custom made for those scopes, just like the switches on DMM's.In my life I've only seen a few rotary switches on the consumer market. Most of those are of not very great quality, and one of superb quality but quite expensive (24 position switch used in switched volume attenuators).The quickest way to get an impression on what sort of rotary switches are on the market is with a picture search:https://duckduckgo.com/?q=rotary+switch&iax=images&ia=imagesI'm guessing here, but your best option may be to add a little DC power supply, a few relays and diodes to devise a matrix to switch your relay's.

author: bob91343
author_rank: Super Contributor
timestamp: June 16, 2019, 10:26:50 pm
content: A 4P4T switch is what you need. There are specialty switches that can do similar jobs but you have to hunt for them. For instance, the switch on a decade box.You can get fancy with relays, of course. Too bulky and expensive. It's unclear how you want to use it. First you say you want to hook 120V to it and later say you want to select capacitors. The latter, of course, is what's done in a capacitance decade box.If you are switching dc, you can connect diodes to select output in a variety of ways. For instance, connect a diode from terminal 2 to terminal 3. In first position, only select terminal 2. In second position, select terminal 3 and the diode conducts to enable terminal 2 as well. Continue the logic for as many positions as needed. This won't work for ac or if you want to conduct current both ways.

author: ArthurDent
author_rank: Super Contributor
timestamp: June 16, 2019, 11:28:28 pm
content: Ian.M is correct that if you try to build this capacitive line voltage charger you are going to hurt or kill someone. You don't even mention diodes, regulation, type of battery, what will happen if a battery fails open or the battery is removed putting full line voltage on the battery leads. If this is your plan on how to build a battery charger you don't have the knowledge to build a safe charger, or any charger, and you should just buy one.

author: shanezampire
author_rank: Contributor
timestamp: June 17, 2019, 12:27:47 am
content: Ian.M: I am setting it up very safe, timer, breakers, and all. Its a battery rejuvenator / desulfator. I know its a very high current DC. I have watched videos of dozens built and read the schematics of dozens of different versions. It for sure will be a thing to respect. Its just all versions use multiple toggle switches to switch on each capacitor. Bigger batteries will need higher uf capacitors / more amps. Some will need less.ArthurDent: I have several battery chargers. 50 Amp all the way down to to 500ma I just wanted to make this particular one. It will be for flooded lead acid batteries. 110v will got to a 6.5uf to a 12.5uf to a 25 uf to a 50uf to a KBPC5010 1000 Volt Bridge Rectifier 50 Amp. (with the capacitor bleeder resistors, fuses, timer, volt meter, amp meter, warning signs, etc and all) This will give me between 1/4 amp to 4 amp depending on which size capacitor I power. I just didn't get all technical cause I was just just looking for a certain switch. The switch could be/have been to feed 110v to any 1 - 4 devices.And I am fully aware that I will have high pulsing current / DC voltage on the ends of bare battery clamps that can and will stop your heart easily. I promise it will not even with a YT video titled "Hey Ya'll, Watch this!"Thanks everyone for taking the time to reply. I guess I will just use the same as everyone else and go with 4 separate toggle switches.

author: Ian.M
author_rank: Super Contributor
timestamp: June 17, 2019, 03:12:48 am
content: That's even worse than I thought. If you used it in any workplace in the USA, OSHA would have your nuts in a vice before you could blink twice, Also knowingly building and using dangerous device, would void any homeowner's or personal insurance policy you are likely to have. If you've got any family, for their sake, *PLEASE* don't build it.

author: bob91343
author_rank: Super Contributor
timestamp: June 17, 2019, 03:49:56 am
content: Check the current and voltage ratings of the switches you intend to use. Otherwise you may be rewarded with a flash of light and the switch will permanently open or close, depending. Fire and smoke also. Have an extinguisher handy.It's true that you may be voiding some portions of your insurance but that depends. Typically you are okay as long as nothing bad happens but if problems arise, the fine print in the policy might get you. I won't comment further.

author: perieanuo
author_rank: Frequent Contributor
timestamp: June 17, 2019, 07:27:26 am
content: 120v ac or dc?for dc, it's simple,diodes from2 to 1 etcaetera.for AC,triacs, same principle.I mever seen one switch with this commutation schemeRegards,pierreEnvoyé de mon iPad en utilisant Tapatalk

author: Zero999
author_rank: Super Contributor
timestamp: June 17, 2019, 10:21:37 am
content: Quote from: Ian.M on June 17, 2019, 03:12:48 amIt's impossible to determine the safety of a project from such a brief description. We don't know the construction details. If it's in a suitable insulated/earthed enclosure, with the appropriate interlocks, then it will be perfectly safe.To answer the original question: use a low power 1P4T switch, with diodes driving four relays or contactors, which actually drive the load. The switches and relay coils can be powered off an isolated 24VDC power supply, which will isolate the operator from the nasty voltages.

author: Ian.M
author_rank: Super Contributor
timestamp: June 17, 2019, 10:52:08 am
content: The O.P. mentions warning signs but doesn't mention enclosure or interlocks. I'd be a lot happier if he had assured us that he was building a fully enclosed battery compartment for it with ex-Microwave door switches or similar for the interlocks.Also I don't like the idea for other reasons - a high open circuit voltage Lead Acid charger significantly increases the risk of internal sparking if a battery has cracked internal inter-cell straps, which can cause a hydrogen explosion that is likely to blow the top off the battery and shower the area with high velocity lead and plastic shrapnel and hot acid. It also increases the risk of external sparking that can be just as dangerous.

author: StillTrying
author_rank: Super Contributor
timestamp: June 17, 2019, 11:44:06 am
content: Quote from: shanezampire on June 17, 2019, 12:27:47 amWhen you connect a cap dropper and bridge rectifier to the mains both of your DC ends are connected to the live mains voltage. Even if charging a 12V battery, both the -ve and +ve ends of the 12V battery are at the full mains voltage.#TooDangerous

author: Zero999
author_rank: Super Contributor
timestamp: June 17, 2019, 12:53:34 pm
content: Quote from: StillTrying on June 17, 2019, 11:44:06 amI don't see anything inherently dangerous about that. It's only dangerous if sensible safety precautions aren't taken. I've seen drill battery chargers with a non-isolated output and they're perfectly safe, because the battery is inside an insulated enclosure and none of the connections are accessible.

author: StillTrying
author_rank: Super Contributor
timestamp: June 17, 2019, 01:09:13 pm
content: Quote from: Zero999 on June 17, 2019, 12:53:34 pmOf course, but the OP's posts mention"very safe, timer, breakers, and all. Its a battery rejuvenator / desulfator."and"I am fully aware that I will have high pulsing current / DC voltage on the ends", but the live AC mains voltage problem, or isolation, doesn't get a mention anywhere.

author: ArthurDent
author_rank: Super Contributor
timestamp: June 17, 2019, 02:24:35 pm
content: Let us not forget that he will, as he said, have 'warning signs' posted to alert everyone that this is a completely unsafe idiotic idea that could result in injury or death.He also said:"I just didn't get all technical cause I was just just looking for a certain switch." Charging lead acid batteries this way without a voltage limit other than line voltage shows a total lack of understanding of the technology or chemistry involved. The voltage should be capped to float at around 13.8 vdc for a '12' volt battery to prevent overcharging.He says: "Its a battery rejuvenator / desulfator". Most lead acid battery cells fail open circuit and won't take a charge. Using this scheme you could have line voltage across an open cell and internal arcing between plates could occur. Maybe he should use this method instead.

author: soldar
author_rank: Super Contributor
timestamp: June 17, 2019, 03:19:18 pm
content: Without entering into the particular use or safety aspects, this is the kind of thing that could be fabricated with some mechanical tools. Some PCB with the correct tracks, some wipers, a shaft, etc. It should not be terribly difficult.It can also be done easily with relays and some circuitry.Even all solid state.Not difficult.Anecdote: I had just moved into my new house and had few tools or components with me. The car battery died. I forget why, maybe i left the lights on. I had no PSU or charger. Somehow I found four 1N4007 diodes.I took an extension cord out to the yard where the car was parked on the wet grass. I connected the neutral to the frame of the car. Using one diode each I connected several lamps to the positive of the battery. I seem to remember I wasn't getting more than about 3 A all together but after a few hours of charging like that I did manage to start the car.The lamps, diodes, cables and bodged connections were obviously dangerous and I put a note and told all my housemates to not touch anything. Even with no note it was quite obvious that it was best to stay away. The battery was charged without any housemates being electrocuted.

author: shanezampire
author_rank: Contributor
timestamp: June 17, 2019, 05:13:56 pm
content: In the video of the battery exploding above... what was the thing on top the battery with the wires running from across the back of the desk to it? Did they just pull the wool over our eyes and fake a hydrogen explosion on us?I am making something very similar to that >

author: ArthurDent
author_rank: Super Contributor
timestamp: June 17, 2019, 06:16:35 pm
content: shanezampire, The video you posted only verifies what posters have been saying about how technically flawed and very dangerous your charging circuit is. Just because it can be posted on YouTube doesn’t mean it is close to being correct and I’d put this video in about the same class as the flat earthers and perpetual energy scams.It is somewhat amusing that you insinuate that the exploding battery video is faked (even though I and many others have seen it happen), but you are willing to swallow everything in the video you posted as fact and reasonable even though it isn’t based on fact or reason.You should read and understand the lead-acid battery charging information in the link below. You should also listen to the warning everyone is giving you on how very dangerous your plan is.https://batteryuniversity.com/learn/article/charging_the_lead_acid_battery

author: Gyro
author_rank: Super Contributor
timestamp: June 17, 2019, 07:32:10 pm
content: Quote from: shanezampire on June 17, 2019, 05:13:56 pmThe OP obviously isn't going to learn from the collective knowledge, advice and warnings. Sometimes sacrifices are necessary in order to provide continued proof that Darwin was right,even in the OP's location.

author: Zero999
author_rank: Super Contributor
timestamp: June 17, 2019, 08:14:30 pm
content: Going from the replies and information posted above, I've changed my position: this is a very dangerous idea. Even if the shock risk can be minimised to a safe level, there's more of an explosion and fire hazard. I wouldn't want a lead acid battery to blow up in my face, showering me with acid.

author: shanezampire
author_rank: Contributor
timestamp: June 17, 2019, 08:34:29 pm
content: I was just simply asking what that was on top the battery and what them wires coming across the back of the desk going to it was? I playing that video full screen on a 26" monitor I could see them clearly. I was just simply curious what it was. I never said it was fake. I believe and know a battery can explode. I have seen batteries explode before.Believe it or not. I am taking in everything you guys are saying. I have been messing with electricity, electrical components, and stuff since I was maybe 7 years old. I have boxes and boxes of stuff I have salvaged over the decades in my shop. I have made may things what work and many thing that didn't. But I have learnt something and walked away with knowledge from the all. I know and hold the knowledge of only maybe 5% of each one of you here.I like to learn, tinker, actually do things. Make things. I could be like one them millennials that sit in mom's basement all day, plays video games, eating Cheetos, thinking they know it all, and scared to go out in the real world and actually do and try things, but I at least came here to ask, listen to the smart and more educated people.But in the end, I am a not build or wired that way. I am not raising my kids that way either. You listen to the smart people, the elders, people with collective knowledge, take advice, adhere to warnings, but don't be scared to actually do and try things.In the end, I am listening to each and everyone of you, making adjustments, but I am still going to build this. I survived riding in the back of an open pick-up truck bed when younger, shooting bottle rockets out of my hand, riding a bike without a helmet, lawn darts, and the many other things that are all now taboo. With caution, I will survive this. I could die in a car accident tomorrow. I know safety and not doing stoopid stuff helps prolong your life but you cant be scared of everything. We are never guaranteed tomorrow.

author: Jwillis
author_rank: Super Contributor
timestamp: June 18, 2019, 04:42:27 am
content: Lead acid batteries while being charged expel hydrogen gas that can cause an explosion.I know this first hand because it happened only a couple feet from my head.Luckily I had a hard hat on at the time and I was positioned in a way that shielded me from the full impact.Caused by near by welding.That being said .The type of switch your looking for is a Multi Step Rotary Switch.These have been used for years in industrial battery chargers with 6 ,12 ,24 and 48 volt configurations without blowing crap up. You just need to know if its AC or DC and the total amps your working with. I don't think they come in a non-shorting (Break before Make) I've only seen Shorting. Good luck.

author: soldar
author_rank: Super Contributor
timestamp: June 18, 2019, 11:48:40 am
content: Lead-acid batteries can release hydrogen and can explode with all sorts of chargers. The dangers of charging with capacitive drop are others.I would only use capacitive drop power supply for very specific things with very low power consumption. I definitely would not use it to charge a battery. Especially when you can buy or make a battery charger for close to nothing. It just makes no sense.