Need help with a switch in a circuit

Thread Starter

Christmas Horse

Joined Nov 6, 2016
6
Hello, I am making a small electric car. I am planning to have a battery connected to a motor with a switch in between. I found a switch in an old toy that is working. I attached a wire to each of the places on the switch where there was an existing wire. However, since I removed the old wires, I have no idea which wires connect to which parts of my circuit. I know 2 wires connect to the positive and negative terminals of my battery, and 2 connect to my motor. I have been doing a lot of trial and error and I can't figure out which way the wires go. The switch has off in the middle, on on one side, and on (reverse) on the other side. I will attach pictures. Thank you.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
I think you are missing the connections to the centre posts. DPDT sw with centre off.
It seems like a simple reverser where you have +-ve going in and a pair to the motor, the switch does the reversing.
Max.
 

Thread Starter

Christmas Horse

Joined Nov 6, 2016
6
I think you are missing the connections to the centre posts. DPDT sw with centre off.
It seems like a simple reverser where you have +-ve going in and a pair to the motor, the switch does the reversing.
Max.
There are 2 small posts coming from the switch that are not soldered to the circuit board... should I try attaching wires to those? And should I attach my battery or motor to those?
Thanks.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
What you need to do is reverse engineer the present switch and PCCT board so that the connections can be actually determined.
Max.
 

MaxHeadRoom

Joined Jul 18, 2013
28,619
Very simple, just trace out the printed circuit on the switch from pin to pin, and sketch it out.
This is very basic to your original post question.
Do you have any kind of test meter?.
Max.
 

Thread Starter

Christmas Horse

Joined Nov 6, 2016
6
Very simple, just trace out the printed circuit on the switch from pin to pin, and sketch it out.
This is very basic to your original post question.
Do you have any kind of test meter?.
Max.
I do not have any test material. I have no other tools other than scissors, a hot glue gun, and a screwdriver.
 

bertus

Joined Apr 5, 2008
22,270
Hello,

@MaxHeadRoom , I have taken the switch part from the last picture posted:

CH_switch_foil.jpg
As you can see there are still two free pins in the middle of the switch.
Also the glueblobs will hide part of the foil trace.

Bertus
 
Oh man, i mastered a DPDT switch yesterday! im a beginner too, took a lil while! I wasnt dealing with a motor but from my understanding 4 switch posts are for he motor and 2 are for the battery when the switch positions are on/off/on for fwd/off/rev outcomes at the motor.

I would leave the two short legs alone and if i had no meter I'd hook 2 left wires to motor and two right to battery. Try all combinations there, if no result then put left on battery and right on motor and repeat til something happens. I may have just given you advixe that will fry something, try at your own risk.

The bit im sure of though, dont worry about connecting the short legs directly to anything - the board will be connecting them somewhere. i suggest prying off the glue so you can see the paths on the board, thats key to whats going on.
 

ericgibbs

Joined Jan 29, 2010
18,766
hi CH,
The Orange goes to the battery positive, the Blue to battery negative.
The White and Yellow go to the Motor.
Wire it up and just touch the Orange wire to the battery positive, it should run OK, then you can attach the wire permanently.

You have not said what the power rating of the new motor is, it maybe to much for small slide switch.
E
 

Phil-S

Joined Dec 4, 2015
238
Switch descriptions are not helped by the phlethora of abrieviations e.g. SPST, SPDT, DPDT, DPST, SPCO, DPCO, plus the many types of action which often depend on which trade uses them. For example, an electrician might refer to a retractive switch, someone else might call it a centre OFF, spring return - "ways", "gangs", "poles" are used interchangeably. "throws" probably comes from the very large "breaker" switches used in industry where literally the operator would throw the paddle from one position to the other - I don't mean throw like a ball, but more to the effort of moving it.
The simplest is the SPST type which is what most people understand by a "switch" - it has two positions for the "paddle", the bit you move physically, ON or OFF - two bits of wire completing a circuit are a SPST.
DP simply means two single switches side by side in the same package operated simultaneously by one paddle. Miniture switches can go up to 4 poles in the same package, sometimes confusingly refered to as 4-way changeover
DT is the same as CO or changeover.
DT allows you to select one of two inputs to one output, i.e. you connect a lamp to the common or centre pin of the switch and you could have either a power supply connected to one of the remaining pins and a battery on the other - the permanently connected switch can be fed by either source, but not at the same time.
Your reversing DC motor can spin in either direction ;depending on the polarity of the supply being fed to it - this why you need a DPDT switch.
The two switch commons go to the motor +ve and -ve while the power supply connects across the same pins of each "pole" and is reversed or cross connected on the other "pole" pins - the direction depends on the paddle position.
The downside of this is that you can't turn the motor off, so for this, you need a DPDT switch with centre OFF.
The most common use of DT or CO switches is in domestic wiring, sometimes called two-way lighting in the UK - so you have one light in the hallway, but can be switched from switches on the landing or the hallway, one lamp with two different sources, same principle. In this case, you would use two SPST switches. Even seasoned electricians can get this wrong, so you aren't alone.
 

Tonyr1084

Joined Sep 24, 2015
7,853
I'm in agreement with ericgibbs. Orange and blue can be connected to the battery in either polarity OR they can be connected to the motor in either polarity. Since the switch does the reversing, regardless of which polarity you choose, the switch will swap them.

The two unsoldered posts can be ignored. However, I have a suspicion that they CAN be utilized as a dynamic brake. But doing so makes it more critical which wires you put on the motor and battery.

A dynamic brake simply shorts the leads together. If you have the dynamic brake wired to the motor then when you turn the switch off the motor will stop hard, as if you put an electric brake on it. But if you accidentally wire it to the battery then you will short out the battery. So it's probably best you leave that part alone.

Personally, I'd opt to put the orange and blue wires on the motor. That way if you ever decide to use dynamic braking you're on the safe side of the switch for that function.

Someone else asked about the motor rating and the switch handling capability. If the motor is much larger than the original motor then you can burn the switch out in short order.

Welcome to the world of electronics. I consider myself a novice too. But I do understand that not only voltages and polarities are important, also power ratings come into play. Way way way back when I was 7 years old I tried to make a variable speed control for a motor with a fan blade on it. I used a potentiometer (called a POT), a battery and a motor. When I turned the motor to full speed it worked. But when I tried to slow the motor down I immediately burned out the POT. Why? Because the pot could handle an eighth of a watt (guessing - I can't possibly remember what its rating was over 50 years ago) and the motor was drawing probably around 5 watts. WAY too much current passing through the device for it to survive.

I'd like to encourage you to continue studying electronics. AAC offers information great for beginners, to help you understand how electricity works, and eventually how to calculate the needs of your circuitry. I suspect you will enjoy messing with electronics very much. I know I do.

And welcome to this forum.

[edit]

Learn how to read schematics. Learning how will help you immensely. And you'll also figure out how to create them. Once you're good with schematics you'll find it much easier to follow the flow of electrons through simple circuits such as your switch.

˚J˚
˘
 

Tonyr1084

Joined Sep 24, 2015
7,853
See if this clears things up for you.

Here are two drawings of the same thing. One as a pictograph and the other as a schematic. The schematic shows two switches connected by a dashed line, indicating that when you throw one switch - BOTH wipers move. The Center Off position is obviously connected to nothing. As I mentioned before, it's possible the center off position may be connected to the two unsoldered posts on your switch. Shorting them will create the dynamic brake I mentioned before. Also the reason why I suggested using the center two posts as connections to your motor and NOT the battery. With a dynamic brake (short circuit) you would short out your battery.

The drawing also shows the typical representation of a motor and a multi-cell battery such as a 9 volt battery. Could be a 12 volt battery, 6 volt - lots of different batteries. However, a single cell such as a AA battery (C or D as well) would be indicated by only a single long line and a single short line. Having groups of two or more represents a multi-cell battery and it's not necessary to show the same number of cells as your battery may actually be.

In the pictogram you see a representation of a 9 volt battery. It's wired to the switch in the same manor the schematic shows. The switch is wired to what appears to be a motor with a shaft long on one side and short on the other. I don't know what motor you have. Either of these diagrams should help you understand better what is going on inside your switch and how you reverse the direction of the motor. For now lets just leave the dynamic braking out of the equation.

Hope this helps.Motor Reversing Switch.jpg
 

Tonyr1084

Joined Sep 24, 2015
7,853
OK, I just noticed that I have my colors reversed. Sorry, the Orange and Blue wires are connected to your center posts of the switch and to the motor. The yellow and white wires should be connected to the battery.

My apologies if my drawing confuses you a little. Just take a little time to decipher the drawing. I'm sure you'll figure it out.
 
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