Help required with switching problem!

[eimaj12000]

Hi,

I'm currently working on a small project for my young nephew. This involves a section of track with rollers geared to work with a small DC motor. Now, here is the tricky part - I need a switching system which will detect a small toy car being placed at one end of the track and engage the motor to roll the car to the opposite end of the track. I want this to work the opposite way also i.e. so that the car placed on the far end of the track trips a switch which reverses the motor and rolls the car along to the other side.

I am not too good with electronics but eager to learn so any help would be much appreciated.

Thanks

 

[mramos1]

You will need to provide a lot more details.

Is this a metal track and it drives the toy via the track? A toy you need to signal which end of the track you are at? Were does the switch go in your plans?

 

[Aily Sajjad]

Hi,
this can be done in a number of ways depending upon how far wish to go. The easiest way is to use a Infra Red transmiter reciever set at both ends to detect the presence of the car.

An micro switch can also be used so that when the car is placed over it, it gets depressed and switches the required action.

Aily

 

[penoy_balut]

you need two micro switches, two dpdt relays one for reverse and another for forward, or even a single relay will do, wire the relays to LATCH (but put some interlock) when micro switches are activated.

 

[eimaj12000]

Hi there,

First of all thank you very much for replying to my post. I pretty much have all the stuff (I think) that I'll need in front of me now, but was wondering if you can help a bit more.

Basically, the way I require this to work is the following:

Two switches (S1 and S2) are used to switch a small electric motor between two directions respectively(clockwise and anticlockwise obviously).

Now, here is the part I'm finding tricky to solve (or indeed understand!). Switches S1 and S2 are positioned as below:

S1-------------------S2
>>>>>>>>>>>>>>>>>>>>> Route 1
<<<<<<<<<<<<<<<<<<<<< Route 2

Route 1 and route 2 here show the path of the toy car over the switches i.e. Route 1 means the car moves OVER S1 engaging the motor and then right to the end of the track passing OVER S2 also. Route 2 is the reverse of this.

I need this to work so that when S1 is pressed the motor goes clockwise until this switch is released BUT ignores the press of S2 and vice versa (car passes over S2, engages motor but circuit ignores press of S1). Also as this is for a kid it would be great to have a safety feature in place whereby having S1 and S2 pressed together would not smoke the thing. Basically I want the thing to work so that when the switches are pressed in the order S1-S2 the motor travels one way and then when pressed in the order S2-S1 the motor travels the other way.

I would be greatly indebted to you if you could help with this as I have bitten off a bit more than I can chew this time.


thankyou for taking the time to read through this and thanks in advance for any help you can offer

 

[mramos1]

How about a DPDT ON-OFF-ON switch. Throw it one way it goes forward, the other is goes backwards? Once part and some wire? Nothing to burn up?

Do you need two switched or one with two throws and a neutral in the middle?

 

[eimaj12000]

hi,

I did look at doing this, but couldn't find a suitable switch (I really want this to work from the toy car being pushed over it so the switch would have to be easily triggered).

I have been trying to make a prototype switch to solve this but am finding it pretty difficult. basically I think one way to get this to work is by taking two of these: **broken link removed**

sticking them together end to end (at the hinge end) and then having only one lever which would basically make a very sensitive (on) off (on) toggle switch but (because we still have two switches) one controls one polarity and one the other. To be honest if I could source a switch like this I'd be very happy - they must exist somehow - basically two switches with a lever in between. the lever going one way triggers one switch and the lever going the other way triggers the other. One of these with a small roller on the lever would be perfect.

Failing that I'm sitting now with DPDT relays and a breadboard with very little electronics knowledge. Be grateful for any help.

 

[penoy_balut]

https://www.electro-tech-online.com/custompdfs/2006/11/acmcc.pdf on page 15, it's the magnetic reversing circuit i'm referring to, when using dc motor polarity is reversed instead of phase and instead of reverse forward pushbutton switches microswitches could be used on both ends

 

[eimaj12000]

Hi, Could I just clarify - you mean page 15 and the AC circuit there ? Would this handle the switching problem of switch S1 triggering the motor but then ignoring the press of switch S2 and vice versa ?

 

[penoy_balut]

no, that's only a basic reversing circuit, in your application you have to add latch, it's a N.O. contact from M1 connected in parallel with forward switch (S1) and N.O. contact from M2 connected in parallel with reverse (S2) switch, in this case when S1 is triggered it will ignore S2 and also S1 and you need to add microswitches to both ends for stopping the motor aside from S1 and S2, when the motor reaches the end , i.e. forward end, it will open the forward stop switch and also closes the reverse start switch

S1 = forward run
S2 = reverse run
S3 = forward stop
S4 = reverse stop

S1 >>>>>>>>>>> S3
S4 <<<<<<<<<<< S2

 

[eimaj12000]

Thanks for this. Just out of interest, how would this be possible with only two microswitches if I could fix it so that S1 would stay pressed until the car reaches the end (obviously S2 would get pressed also).

Also, I'm very interest to solve the following problem which has come from this:

If I put two microswitches together with a lever hinged in between to essentially make a sensitive (on) off (on) toggle switch I can have a system whereby an object passing over the switch in one direction causes the DC motor to turn in one direction and then off when the object leaves the switch and vice versa for the object moving in the other direction. Basically, a sensitive lever operated toggle switch with two on positions (one for each polarity). Can you buy these things ready made as this would solve another problem on this project for me ?

Thanks again

 

[eimaj12000]

Ok - here's the clincher:

If I some kind of circuit with two switches:


S1 S2


How can I make it so that the switches pressed in the order S1 - S2 will turn something on but when switched in the S2 - S1 order will not work ? Note that here I require the circuit to operate ONLY while the switches are pressed. Please can someone help with this as I'm sure it's an elemntary problem to you guys ?????


Thanks in advance