Ah. Yes you are correct there, I thought it was the other way round

Here are the two circuits I've described.

1 - has the same operating polarity as described in post #1.Q1 acts as an emitter follower, not a saturated switch, so its Vbe is in series with the relay coil. This is why you must be sure the relay will operate reliably with only 4 V on its coil.

2 - is operationally the same as #1, but in this circuit the relay driver transistor Q3 is acting as a saturated switch, so almost the entire 5 V appears across the relay coil. A variation of this circuit uses two identical NPN transistors, but is much less efficient in the off state.

ak
View attachment 225917

Hi
Thanks for the info, the ir receiver I have has 3 leads , not sure how they fit to the drawings you have posted !.
Spike

 

Is this for the paper shredder.. again...

View attachment 225908

What does the 7 mean after the 4K R ! .
Spike

 

What does the 7 mean after the 4K R ! .
Spike

4k7 = 4.7 kΩ = 4,700 Ω

The k acts like a decimal place (or comma depending on area), as does and R, for example 4R7 = 4.7 Ω.

 

4k7 = 4.7 kΩ = 4,700 Ω

The k acts like a decimal place (or comma depending on area), as does and R, for example 4R7 = 4.7 Ω.

Tks , should of known that, learn something every day .
Spike

 

Here's a circuit using one PNP as a saturated switch so the relay coil voltage is near 5V when ON.

 

, the ir receiver I have has 3 leads , not sure how they fit to the drawings you have posted !.

As long as information about the component is secret, neither do I.

ak

 

As long as information about the component is secret, neither do I.

ak

Ah, yes, will have to find that info.
Cheers
Spike

 

Here's a circuit using one PNP as a saturated switch so the relay coil voltage is near 5V when ON.

View attachment 225984

Thank you.
Spike

 

As long as information about the component is secret, neither do I.

ak

Hi
Here is the info on the IR Emitter and Receiver.

https://media.digikey.com/pdf/Data Sheets/Adafruit PDFs/2168_Web.pdf
Spike

 

Here's a circuit using one PNP as a saturated switch so the relay coil voltage is near 5V when ON.

View attachment 225996

This is the ir receiver I have .
https://media.digikey.com/pdf/Data Sheets/Adafruit PDFs/2168_Web.pdf

 

Ah. Yes you are correct there, I thought it was the other way round

If you just want to drive a 5v,70ma relay, the sensor output can sink 100ma, so the relay coil can be connected directly to the sensor output. Connect the other end of the relay coil to +5v. Connect a diode across the relay coil (cathode to +5, anode to sensor output side of coil). When the sensor activates, the relay coil will energize.

 

If you just want to drive a 5v,70ma relay, the sensor output can sink 100ma, so the relay coil can be connected directly to the sensor output. Connect the other end of the relay coil to +5v. Connect a diode across the relay coil (cathode to +5, anode to sensor output side of coil). When the sensor activates, the relay coil will energize.

Hi
Yes, tks, that is what I was wanting initially, but I wanted to use the Receiver output to ground to switch a trans on, because I thought the 70mA of the relay was a bit too near the max 100mA of the receiver, so just wanted a bit of room there and would take the load of the Receiver ! .
cheers
Spike

 

Translated from the datasheet:

Model: QT50CM Technical parameters:
1. Induction distance: 50cm
2. Induction method: through-beam type (non-transparent)
3. Working voltage: DC3.0VDC-5.5VDC
4. Working current: 10MA
5. Output method: 0V or 5VNPN/PNP Open (normally closed to be customized)
6. Output current: 100mA (can directly drive the relay)
7. Transmitting angle: straight line (infrared light)
8. Receiving angle: <10 degrees
9. Response time: 2ms
10. Working temperature: -25 degrees 60 degrees
11. Working environment: indoor (not waterproof)
12. Dimensions: length 2cm, width 1cm, height 0.9cm
13. Cable length: 15cm Transmitting: red wire = 5VCC / black wire = GND receiving: red wire =5VCC/black wire=GND/yellow wire=OUT(NPN)

https://cdn-shop.adafruit.com/product-files/2168/C2917.pdf

Bertus

 

Hi
Yes, tks, that is what I was wanting initially, but I wanted to use the Receiver output to ground to switch a trans on, because I thought the 70mA of the relay was a bit too near the max 100mA of the receiver, so just wanted a bit of room there and would take the load of the Receiver ! .
cheers
Spike

I think there's enough headroom to not worry, but I appreciate that you do.