There are some wonderful photo-transistor sensors that include the amplifier electronics and everything all in one of those small transistor cases, and they will work with either a bright LED or a cheap laser. And the output is TTL compatible so it can drive a transistor directly and that can operate the relay. The part is made by both Fairchild and Honeywell, and probably others as well.

 

Here is a circuit using a 555 as a switch , supply is 5 to 15V, the relay clicks on when blocked.

View attachment 224143

Hi again
Is there any spec for the ir emitter and receiver, have some pairs of each, but don't know the voltage of them ! .

cheers
Spike

 

Not really, as long as they are on the same wavelength of light spectrum, just lower the series resistor on the led to increase the led current/brightness distance.

 

Not really, as long as they are on the same wavelength of light spectrum, just lower the series resistor on the led to increase the led current/brightness distance.

Hi
Thanks for your reply.
Spike

 

Depending on the circuit selected, breaking the beam can either operate or release the relay. So you do need to decide which way you want it to operate.
And how good is your understanding of electronic circuits?
And last, there is a website that is about 100dB better than yootoob for circuit information.
That is "Schematicsforfree" . You will find a lot of photo-electric circuits there, some simple and some complex.

 

Depending on the circuit selected, breaking the beam can either operate or release the relay. So you do need to decide which way you want it to operate.
And how good is your understanding of electronic circuits?
And last, there is a website that is about 100dB better than yootoob for circuit information.
That is "Schematicsforfree" . You will find a lot of photo-electric circuits there, some simple and some complex.

Hi
Thanks for your feedback , I need the break beam to operate the relay .I am doing the schematic “ dodgydave” drew for me !
Will def look at that site you mentioned though .
Cheers
Spike

 

Here is a circuit using a 555 as a switch , supply is 5 to 15V, the relay clicks on when blocked.

View attachment 224143

Hi
Could I use a IN5392 Diode in place of the IN4001 ! .

Cheers
Spike

 

I have a TX/RX unit on my desk right now. It came from an old tape recorder player. It has a space (gap) of 5mm. And that's about the biggest I've seen. The date code on the PCB is 1098, meaning the PCB was made the 10th week of 1998. So this one is 22 years old. I took it out of a defunct Sony stereo, dual cassette player recorder.

https://produto.mercadolivre.com.br...84-zg1-652-61-84-zg1-653-61-84-zg1-606-01-_JM
It actually came up searching that number on the bottom. However it's in a foreign language, one I don't recognize or understand.

 

Hi
Could I use a IN5392 Diode in place of the IN4001 ! .

Cheers
Spike

Yes any fast acting diodes.

 

Yes any fast acting diodes.

Hi
Thanks for that.
cheers
Spike

 

I am still wondering why anybody would suggest using a timer IC instead of a single transistor, or a single darlington transistor?
With enough gain, a single NPN transistor works well. The relay coil connects between the collector and the positive supply, the emitter is connected to the supply negative side. A fairly high value ( start with 100K ohms) resistor is connected from the positive supply to the transistor base. So when the photo device switches off the base is pulled high, and the relay operates.
The photo sensor, such as a photo-transistor, is connected between the transistor base and emitter, so that when it conducts the base is pulled low. This keeps the transistor switched off.
Select a transistor adequate for the supply voltage and for the relay current, with enough gain to operate the relay when the base is not pulled down. The resistor limits the on-state base current.

To power the LED you need a series resistor to drop about 22 volts with a current of 20 milliamps. R=E/I = 22v/20 mA=1.2K ohms.

So there is a bit of math needed and also looking at data sheets. But tyewhole circuit only needs five terminals and one resistor. The diode is usually not needed because the current change in the coil is not that fast.

 

I am still wondering why anybody would suggest using a timer IC instead of a single transistor, or a single darlington transistor?
With enough gain, a single NPN transistor works well. The relay coil connects between the collector and the positive supply, the emitter is connected to the supply negative side. A fairly high value ( start with 100K ohms) resistor is connected from the positive supply to the transistor base. So when the photo device switches off the base is pulled high, and the relay operates.
The photo sensor, such as a photo-transistor, is connected between the transistor base and emitter, so that when it conducts the base is pulled low. This keeps the transistor switched off.
Select a transistor adequate for the supply voltage and for the relay current, with enough gain to operate the relay when the base is not pulled down. The resistor limits the on-state base current.

To power the LED you need a series resistor to drop about 22 volts with a current of 20 milliamps. R=E/I = 22v/20 mA=1.2K ohms.

So there is a bit of math needed and also looking at data sheets. But tyewhole circuit only needs five terminals and one resistor. The diode is usually not needed because the current change in the coil is not that fast.

Yes that would work just as well, but the 555 that I suggested has built in Hysteresis to prevent relay chatter.

 

Yes that would work just as well, but the 555 that I suggested has built in Hysteresis to prevent relay chatter.

A relay in this application should not chatter. The operate and release current values are quite different.

 

Hi
Has per " dodgydave" schematic, is there anyway that I could add a "Delay" in the circuit, so that when the relay is activated it will stay on for a second or so after the object has passed the ir break beam sensors ?.
Was thinking of putting a cap in there ! .
cheers
Spike

 

Schematic as per last drawing

 

Here is a circuit using a 555 as a switch , supply is 5 to 15V, the relay clicks on when blocked.

View attachment 224143

Hi
What about this , with relay time delay included ! .
Spike

 

Hi here is a modified circuit giving you a 2 second delay after paper clear, you can alter the delay by changing the 22uF cap and the 100K resistor.

 

Hi here is a modified circuit giving you a 2 second delay after paper clear, you can alter the delay by changing the 22uF cap and the 100K resistor.

View attachment 225082

Hi
Thanks for your reply, this ok ! .
ps: Cap should read 22uf not 2.2uf .
cheers
Spike