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photo-interrupter circuit

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carlson

New Member
I know very little about electronics even though I was an electrician once.

I have this little circuit as a train interrupter.

Silicon Chip Online - Circuit Notebook

I wish to change it to switch "off" when interrupted, to operate it on 5 volt, and preferably for the transistor to switch another 5 volt 1 amp positive circuit directly by a bigger transistor instead of by the relay.

A simple problem for any guru I'm sure.

I look forward to your reply
 

ericgibbs

Well-Known Member
Most Helpful Member
I know very little about electronics even though I was an electrician once.

I have this little circuit as a train interrupter.

Silicon Chip Online - Circuit Notebook

I wish to change it to switch "off" when interrupted, to operate it on 5 volt, and preferably for the transistor to switch another 5 volt 1 amp positive circuit directly by a bigger transistor instead of by the relay.

A simple problem for any guru I'm sure.

I look forward to your reply
hi,
The 4093 ic has 4 gates in the package, to invert the signal add a spare gate in series with the existing 4093 gate.

What is the 5V 1A power transistor you want to add, going to switch.??
 

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carlson

New Member
"hi,
The 4093 ic has 4 gates in the package, to invert the signal add a spare gate in series with the existing 4093 gate.

What is the 5V 1A power transistor you want to add, going to switch.??"



I am going to switch this bi-polar stepper motor circuit

Silicon Chip Online - Circuit Notebook

The stepper motor is 5 volt so will power all at 5 volt.

This stepper motor circuit only has the one spare gate which I will be using so I'd don't have a second spare gate.

Only switching the motor controls off leaves the mosfets powered causing mosfet overheating.

I therefore want to switch just the mosfets off.

I would then manually restart the motor perhaps with a momentary switch across a 1 amp larger transistor or the emitter collector of the Photo interrupter. This would re-power the motor circuit with the Photo interrupter then holding the circuit on until the photo interrupter again detects and switches the circuit off.
 

carlson

New Member
The photo interrupter will be cut in half and used in reflective.

Any issues with using this way in the circuit compared to normal.

Thank you for your help
 

carlson

New Member
The photo interrupter will be cut in half and used in reflective.

Any issues with using this way in the circuit compared to normal?

Thank you for your help
 

ericgibbs

Well-Known Member
Most Helpful Member
The photo interrupter will be cut in half and used in reflective.

Any issues with using this way in the circuit compared to normal?

Thank you for your help
hi,
Have a look at this option.
 

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carlson

New Member
Thank you very much guru eric

What would be the resistor values if the photo interrupter is at 5 volt as well
 

ericgibbs

Well-Known Member
Most Helpful Member
In this original circuit

Silicon Chip Online - Circuit Notebook

removing the schmitt changes the output from closed to open, so turns off the relay instead of turning it on when the "beam" is blocked

Is the circuit still "good electronics" without the schmitt?

If not what is required?
hi,
The schmitt will stop any chatter of the relay [ or other following circuit]
Keep it in the circuit.

Is the first transistor after the schmitt still a bc337
Yes.

The 100R at 5V-0.7V = 4.3/100 =43mA.

So 4.3V * 0.043 = 0.18Watt , I would use a 0.25W or 0.5W resistor, the other resistors are 0.125W
 

carlson

New Member
I have a 220R at photo led base giving 1.2 volt acoss led

A variable at emitter 0-500R set runs best about 220R and gives variable sensitivity on photo receiver

I therefore have input and output circuit at 5 volts

However the load is not switching.

Could you confirm the resistor ratings and suggest which might be variable and from what values in order to trigger load as original circuit worked nicely but you attached circuit doesn't

Thank you for your attention
 

ericgibbs

Well-Known Member
Most Helpful Member
hi,

Rechecked my circuit. looks OK.

Ran a LTSpice simulation, works fine, The plot shows the V and I in the output load.
 

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ericgibbs

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Most Helpful Member
I have a 220R at photo led base giving 1.2 volt acoss led

A variable at emitter 0-500R set runs best about 220R and gives variable sensitivity on photo receiver

I therefore have input and output circuit at 5 volts
I am working on the circuit you originally you posted, what are these changes referring too.???
 

carlson

New Member
Changes are only from 12v to 5v on photo interrupter which I've handled with 220R's

The tip32 does switch a piezo buzzer and a 6v relay.

The tip32 does not fully turn on a 750ma 5 v incandescant lamp.
The tip32 gets warm and the lamp only just glows.

Therefore I cant see it switching the 1 amp stepper motor circuit

Please advise

Thanks in anticipation
 

ericgibbs

Well-Known Member
Most Helpful Member
Changes are only from 12v to 5v on photo interrupter which I've handled with 220R's

The tip32 does switch a piezo buzzer and a 6v relay.

The tip32 does not fully turn on a 750ma 5 v incandescant lamp.
The tip32 gets warm and the lamp only just glows.

Therefore I cant see it switching the 1 amp stepper motor circuit

Please advise

Thanks in anticipation
hi,
Please post a diagram.:)
 

carlson

New Member
It is exactly as per your thumbnail circuit posted above at 12.59 yesterday. The only changes are the 2 photo interrupter resistors are 220R and the 12v and 5 v rail are a common 5v rail.

Changing the resistors to tip32 give increased power but maths not my strong point so I dont know what resisters would give me the 1amp I require.

Otherwise the circuit works perfectly including turning off when interrupted.
The chatter if relay is the load and schmitt is removed is as you say so I have left schmitt in circuit as advised.

Just a 1amp output is the issue now
 

carlson

New Member
It is exactly as per your thumbnail circuit posted above at 12.59 yesterday. The only changes are the 2 photo interrupter resistors are 220R and the 12v and 5 v rail are a common 5v rail.

Changing the resistors to tip32 give increased power but maths not my strong point so I dont know what resisters would give me the 1amp I require.

Otherwise the circuit works perfectly including turning off when interrupted.
The chatter if relay is the load and schmitt is removed is as you say so I have left schmitt in circuit as advised.

Just a 1amp output is the issue now
 

ericgibbs

Well-Known Member
Most Helpful Member
What type of transistor have you used where the dwg shows a 2N2222.?
 
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