spdt switch - Page 1
Forum section: electronics / beginners

author: fixit7
author_rank: Regular Contributor
timestamp: May 21, 2019, 01:01:54 am
content: I have working circuit using my breadboard.I used a full size spdt switch to turn the circuit on.I ordered a switch to plug into the board to replace it, but it will not work.Are there more than one type?Andy

author: MarkF
author_rank: Super Contributor
timestamp: May 21, 2019, 01:07:12 am
content: Without any details of what the requirements are...I have used these to switch signals and low current and voltage power lines.https://www.digikey.com/products/en?keywords=EG2459-NDEdit - These have gold contacts if that is a concern.

author: Audioguru
author_rank: Super Contributor
timestamp: May 21, 2019, 01:13:36 am
content: Most switches are made for high currents at the mains voltage so they have silver contacts. But for low voltage and low currents it fails when it becomes corroded.Therefore I use switches with gold plated contacts for low levels, these switches do not cost more.

author: SL4P
author_rank: Super Contributor
timestamp: May 21, 2019, 01:57:14 am
content: The pinout May be different.Some have the wiper in the middle, some to one side.

author: Brumby
author_rank: Unknown
timestamp: May 21, 2019, 04:57:40 am
content: Quote from: fixit7 on May 21, 2019, 01:01:54 amThere are thousands of different types of switches, but for any given style, there can be a variety of configurations.But, in all honesty, you haven't really given us enough information to provide a clear answer to your question.

author: fixit7
author_rank: Regular Contributor
timestamp: May 21, 2019, 11:25:20 am
content: 3-Pin SPDT Slide SwitchNumber of pins: 3Contact form: SPDTSwitch function: ON-ONContact rating: 0.3A @ 125VACDimensions: 0.45"L x 0.16"W x 0.24"DLead spacing: 0.1" (2.54mm) - Breadboard friendlyHousing material: PlasticLead length: 0.24"Actuator height: 0.12"Actuator travel: 0.1"PCB mounthttps://www.dropbox.com/s/m3hq985tsujucsm/20190521_062111.jpg?dl=0

author: Ruaeh123
author_rank: Newbie
timestamp: May 21, 2019, 12:51:56 pm
content: The situation puts three main possibilities on the table:1. The switch is faulty2. You have connected your circuit between the two throws3. Your circuit is non-functonal for whatever reasonThe first thing I would do is, as SL4P said, check the pins with a multimeter in continuity mode to figure out the pinout and check if the swhitch is good or faulty.There should be a combination of two pins that doesn't have continuity in any of the two positions of the switch(since these ate the two throws) and any other combination would have continuity in one of the two positions of the switch.This will check the veracity of the first two possibilities, and if that's the case, the switch it's not the colpritI hope I have been helpful

author: Brumby
author_rank: Unknown
timestamp: May 21, 2019, 04:05:29 pm
content: That's terrific info! (A bit more than needed - but too much is better than not enough!)The classic operation of such a switch is there should be continuity between the centre connection and either of the two end connections, depending on which end the actuator is placed.In the photo you provided () with the switch actuator at the left (as shown) you should have continuity between the centre connection and the left connection. With the switch actuator moved to the right, you should have continuity between the centre connection and the right connection. If this is not the case, then it would seem you have a faulty switch.

author: exe
author_rank: Unknown
timestamp: May 21, 2019, 04:23:57 pm
content: Just use multimeter to troubleshoot it.

author: ebastler
author_rank: Super Contributor
timestamp: May 21, 2019, 04:29:40 pm
content: I assume you are using a solder-less breadboard, where you just plug your components in from the top. Having looked at the picture of the switch which you provided via Dropbox -- do these contacts really fit into the breadboard sockets? They look like rather wide metal tabs, meant to solder wires to them.How did you fit the switch to your breadboard? Are you sure it is making proper contact with the breadboard? Again, a multimeter will help you to diagnose this.

author: MarkF
author_rank: Super Contributor
timestamp: May 21, 2019, 04:38:35 pm
content: Is the switch not working?ORAre you looking for a replacement switch for a breadboard?If so, what kind of breadboard? Solderless or a prototype-board?

author: fixit7
author_rank: Regular Contributor
timestamp: May 21, 2019, 06:05:58 pm
content: Quote from: MarkF on May 21, 2019, 04:38:35 pmWith the larger switch, I soldered to the pins and ran the ends to my breadboard.

author: fixit7
author_rank: Regular Contributor
timestamp: May 21, 2019, 06:17:45 pm
content: Quote from: Ruaeh123 on May 21, 2019, 12:51:56 pmIt was no. 1.Switch was faulty.

author: fixit7
author_rank: Regular Contributor
timestamp: May 21, 2019, 07:09:59 pm
content: Not sure now.The switch sometimes works, but most often does not.Here is where it is used in.When a laser is shined on the cadmium photocell, the alarm does not sound.When the beam is interrupted, it sounds.When I use the larger 3 amp switch, the circuit always works?

author: Audioguru
author_rank: Super Contributor
timestamp: May 21, 2019, 07:28:42 pm
content: The switch is faulty because its contacts are made for up to 300mA at 125VAC (peak voltages are 177V). But again, your schematic does not show the resistance value of R1 which probably has a current that is 1 millionth what the switch needs and your pin 2 voltage is 60 times too low for that high power switch. Use a switch with gold contacts made for low power.Is the function of the switch to turn off the beeper when you want after it has been triggered?

author: fixit7
author_rank: Regular Contributor
timestamp: May 21, 2019, 08:06:23 pm
content: Quote from: Audioguru on May 21, 2019, 07:28:42 pmResistor is 220 ohms.Switch does turn off beeper when it is triggered.

author: Zero999
author_rank: Super Contributor
timestamp: May 21, 2019, 08:42:58 pm
content: Why not put the switch in series with the entire circuit, rather than just the beeper?Audioguru is mistaken about switches corroding, when the current and volt are too low. Using a switch at too lower voltage and current will not break it, but he does have a point that it might be unreliable. Switches with copper or solver contacts need to have a high enough voltage and current to ensure the oxide layer is broken, when the contacts make. This is known as the wetting current. If the current is too low, then the switch might not operate reliably. The solution is to use a switch with gold plated contacts, which doesn't suffer from this issue because gold doesn't oxidise.

author: Brumby
author_rank: Unknown
timestamp: May 22, 2019, 01:51:59 am
content: It's a slide switch. The mechanical action of contacts sliding should be more than enough to break any oxide layer unless it is excessive. Long term storage in less than ideal conditions could cause that. Then there is the possibility of other contaminants getting onto the contact surfaces.Both of the above conditions can sometimes be rectified by operating the switch several times, possibly in conjunction with a switch/contact cleaner.If this doesn't fix things, then the switch would seem to have a more severe mechanical fault.The other thing you can do (if you haven't already) is to try the two combinations available (centre and left -or- centre and right) and see if one is reliable.

author: fixit7
author_rank: Regular Contributor
timestamp: May 22, 2019, 02:15:02 am
content: Quote from: Zero999 on May 21, 2019, 08:42:58 pmI am not sure how to put the switch in series with the circuit.The switches connects with pins 2 and 3 of the 555 chip.

author: Brumby
author_rank: Unknown
timestamp: May 22, 2019, 02:33:14 am
content: The suggestion means joining pins 2 and 3 of the 555 and putting the switch in the power to the circuit so that the whole circuit is turned on or off.

author: fixit7
author_rank: Regular Contributor
timestamp: May 22, 2019, 11:32:36 am
content: I should have shown this earlier.https://www.dropbox.com/s/0dyg6wogy341lhd/KEEP_circuit.jpg?dl=0I have a 3rd wire going from switch to the negative of the buzzer.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 22, 2019, 11:44:18 am
content: Your photo shows a DOUBLE pole, double throw (DPDT) switch. But your circuit is using only one "pole". It is common to see double pole switches connected with the poles in parallel. That provides a rather more reliable action for small-signal applications like yours. I would strap the sections in parallel if you don't need double-pole operation. Old-school open slide switch designs like that are not necessarily reliable for very low power applications.

author: ebastler
author_rank: Super Contributor
timestamp: May 22, 2019, 12:16:53 pm
content: Quote from: Richard Crowley on May 22, 2019, 11:44:18 amI see a SPDT switch, and a shadow.

author: fixit7
author_rank: Regular Contributor
timestamp: May 22, 2019, 03:12:03 pm
content: Quote from: Richard Crowley on May 22, 2019, 11:44:18 amI must need a double pole switch because when I substituted a spdt switch, the circuit stopped working correctly.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 22, 2019, 03:13:12 pm
content: Quote from: fixit7 on May 22, 2019, 03:12:03 pmThat makes no sense at all. Your circuit clearly shows a SINGLE pole, double throw switch.

author: soldar
author_rank: Super Contributor
timestamp: May 22, 2019, 03:19:56 pm
content: Quote from: ebastler on May 22, 2019, 12:16:53 pmI see a SPDT switch without a shadow of a doubt

author: ebastler
author_rank: Super Contributor
timestamp: May 22, 2019, 03:37:15 pm
content: Quote from: fixit7 on May 22, 2019, 03:12:03 pmNow I'm confused. Which switch are you actually using?I am referring to this photo which you share in reply #5:https://www.dropbox.com/s/m3hq985tsujucsm/20190521_062111.jpg?dl=0That is an SPDT switch. (Single pole, two positions, each positions connects the single pole in the middle to one of the outer contacts.) Did you share some other picture which shows a dual-pole switch?

author: fixit7
author_rank: Regular Contributor
timestamp: May 22, 2019, 03:57:30 pm
content: Richard said he saw a dpdt switch ?

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 22, 2019, 04:13:12 pm
content: Quote from: fixit7 on May 22, 2019, 03:57:30 pmI was referring to the photo cited in #5, but I confused the shadows of the terminals for the other set of terminals if it were a DPDT switch. How sloppy of me.In any case, the circuit cited in #13 clearly shows only a SPDT switch.

author: fixit7
author_rank: Regular Contributor
timestamp: May 22, 2019, 04:29:24 pm
content: Quote from: Richard Crowley on May 22, 2019, 04:13:12 pmOk. I would like to get a switch that I can use on my breadboard.I was told to find one with gold contacts, but could not find any.Only larger switches with gold contacts.

author: Gyro
author_rank: Super Contributor
timestamp: May 22, 2019, 04:37:51 pm
content: One solution is to mount your breadboard on a base board and fit a vertical panel for mounting switches, terminals etc.DIP switches have the same footprint as DIP ICs and have gold plated contacts, two (possible) problems though...1. The pins might be a bit too thin to make a reliable connection with the breadboard contacts and2. Because they are so small, you need a pointer to switch them.Fitting a base and front panel is the better longer term solution.

author: MarkF
author_rank: Super Contributor
timestamp: May 22, 2019, 04:46:36 pm
content: Quote from: fixit7 on May 22, 2019, 11:32:36 amI don't see how your 555 timer ever works.It should be something like:Quote from: fixit7 on May 22, 2019, 04:29:24 pmThe one I posted earlier for solderinghttps://www.digikey.com/products/en?keywords=EG2459-NDOr this one for a solderless breadboardhttps://www.digikey.com/product-detail/en/e-switch/100SP1T1B1M51REH/EG2354-ND/378823

author: MarkF
author_rank: Super Contributor
timestamp: May 22, 2019, 05:00:59 pm
content: Quote from: Richard Crowley on May 22, 2019, 04:13:12 pmThe circuit in post #13 is invalid.Please post your pictures into the forum as an attachment. Do not use DropBox.I have seen many pictures go away because they were linked to other services.

author: fixit7
author_rank: Regular Contributor
timestamp: May 22, 2019, 05:42:31 pm
content: I fixed the picture in post #13.