Switch with three positions - Page 1
Forum section: electronics / beginners

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: February 17, 2016, 05:39:29 pm
content: 1. I have to search for switch which has three positions: off, medium, high. Voltage is 220Vac & current is around 400mA.Off means no connection to load, medium means connection to load via a diode in series & 220v ac main(half wave), & high means entire main connection to load.2. I have found a switch from local market as in attached pdf. But it has four positions. It has total 10 pins on it. 5 on each side.There is one common connection on each side, which make connection with other 4 terminals, as switch is toggled.3. What do these switches called, are these Dual pole 4 throw?? I am looking for three position switch. i dont know what name to search for these switches? I need this kind of switch whose handle is on top as in attached pdf.

author: Ian.M
author_rank: Super Contributor
timestamp: February 17, 2016, 05:51:18 pm
content: The gaps between the contacts are insufficient for 220V AC, and as its a slide switch, the contacts don't have a 'snap' action so open too slowly to be safe switching 220VAC, as they will arc and burn up. Slide switches like that are only suitable for low current low voltage circuits. The only way you could use one would be to use it to control two relays with low voltage coils and mains rated contacts to control your load.I assume this is related to yourhttps://www.eevblog.com/forum/beginners/quarter-wave-rectifier/topic.

author: hamzadis
author_rank: Newbie
timestamp: February 17, 2016, 05:57:32 pm
content: The switch in your photo is called a slide switch. You can find ones with 3 positions on ebay, such ashere.You can also findtoggle switches,rocker switchesorrotary switcheswith 3 positions. For some of them, one of the positions will be "off", as no pins will be connected together.

author: SL4P
author_rank: Super Contributor
timestamp: February 18, 2016, 07:06:09 am
content: Keep in mind - no matter how small the load passing through... that switch has a metal body, is unlikely to be mains rated, and any internal failure will brighten up your day for a moment. Then darkness.It may say 220V 3A in the stamping, but I wouldn't let it anywhere near mains AC with me holding the handle.

author: ali6x944
author_rank: Frequent Contributor
timestamp: February 18, 2016, 07:49:51 am
content: Why not use relays?If u r asking about how to turn them on, the answaer is using a cap voltage divider and a bridge rectifyer then your switch in between, what do u think, tell me your opinion belowHope u find what u r looking for

author: Richard Crowley
author_rank: Super Contributor
timestamp: February 18, 2016, 08:12:18 am
content: This is the kind of switch you need for your requirements...http://www.ebay.com/itm/AC-250V-15A-SPDT-3-Screw-Terminals-3-Positions-ON-OFF-ON-Mini-Toggle-Switch-/231326470829

author: ali6x944
author_rank: Frequent Contributor
timestamp: February 18, 2016, 08:24:22 am
content: I thing go with the switch its simpler choice

author: Ian.M
author_rank: Super Contributor
timestamp: February 18, 2016, 09:36:27 am
content: I certainly wouldn't advocate a capacitive dropper or other non-isolated supply to power relays controlled by a slide switch. Direct acting slide switches in general are unsuitable for use above 50V, and most are unsafe above that voltage. As such, a fully isolated low voltage supply would be required.If the center off toggle switch protrudes too much, another option would be a dual rocker switch. If its got SPDT or SPST sections, one would switch power and the other the diode, but if one with DPDT sections is used, its possible to wire it so either section gives half power and both together give full power.

author: krish2487
author_rank: Frequent Contributor
timestamp: February 18, 2016, 10:52:53 am
content: Quote from: Richard Crowley onTodayat 07:12:18 PM

author: Gyro
author_rank: Super Contributor
timestamp: February 18, 2016, 01:37:16 pm
content: Alternatively you may be able to get away with two 2-way rocker switches side by side (as used for controlling heat settings on heaters, hairdryers etc). It depends on the application.

author: johnkenyon
author_rank: Regular Contributor
timestamp: February 18, 2016, 05:44:07 pm
content: Quote from: Gyro on February 18, 2016, 01:37:16 pmConsider using a larger switch for on-off, and a smaller one for medium/high.That way you have a positive "off" position that can be identified by touch, and is less likely to be mis-operated.A centre off switch could leave a user who wants to go "medium" > "off", accidentally going "medium" > "high" if the switch is thown all the way to the other side.

author: Ian.M
author_rank: Super Contributor
timestamp: February 18, 2016, 06:22:02 pm
content: Further to the two rocker switches suggestion. If each feeds the load via its own diode, with the diodes in opposite directions, if either is on you get half power and if both are on you get full power, but its possible to use cheap SPST switches.

author: Vindhyachal.takniki
author_rank: Frequent Contributor
timestamp: February 19, 2016, 12:47:54 pm
content: How about using the switch which is attached, it says 250vac/10A. I will select DP3T.In my circuit entire load is resistive+one 1N4007+500K resistor+led(as in tester)

author: Ian.M
author_rank: Super Contributor
timestamp: February 19, 2016, 01:08:48 pm
content: It depends. Some of those switch configurations certainly wont have a 250V AC rating.If the slider fully covers the opening in the switch body in all positions and it has a strong snap action, then yes a 250V AC rating is possible. You will need to check the individual switch ratings to see if there is a double pole three position one for 250V AC

author: ali6x944
author_rank: Frequent Contributor
timestamp: February 19, 2016, 03:48:54 pm
content: Wait guys, does the contacts of this switch arc?At this current and voltage I'm affraed that the switch contacts would decaey as it being switched, if it an inductive load, correct me if am wrong