- #36
jbord39
- 74
- 0
Thanks for the reply. I'll work on the circuits and get back :)
Building a Circuit to Switch On/Off a 9V Motor
In summary, the conversation discusses the issue of building a circuit that switches on and off another device using an IR LED and a phototransistor. However, the circuit is not working as expected and there are suggestions for adding a latching relay to the circuit. The conversation also delves into the concept of modulating the IR LED for better range and the possibility of using a 38 kHz IR detector to operate a relay or switch. The conversation ends with the suggestion of using a 38 kHz IR receiver chip and a 10 turn pot for the 10K resistor for better control.
- #37
jbord39
- 74
- 0
Here is the finished schematic for the controller with pictures. Thanks for the help everyone...
Now to make the car.
Now to make the car.
- #38
thebeaverwhis
- 2
- 0
I also am interested in this circuit,I am basically doing the same thing,but my beam is a shorter distance( 10 - 12 ") and will be operating a small dc motor( 1.5- 9vdc) so this circuit has capability to run motor without a relay?
- #39
I_am_learning
- 682
- 16
Hi jbord39,
In your latest circuit, the Green Led can never be ON.
Also, if Your 555 can work with 9V, why use 7805. It will continuously drain current from the battery. You could just eliminate it, and use 9V instead.
You haven't shown any resistors in the Left sides of the 555. You would need one to the Base of first transistor and in series to collector of second transistor. Otherwise, too high currents will flow, not good for Leds.
If you have already used this circuit then the IR LEDs are already damaged or atleast <what I would like to call> abused.
It means, they aren't dead, but they produce too little light from too high current.
Try using fresh Leds and use resisters always.
In your latest circuit, the Green Led can never be ON.
Also, if Your 555 can work with 9V, why use 7805. It will continuously drain current from the battery. You could just eliminate it, and use 9V instead.
You haven't shown any resistors in the Left sides of the 555. You would need one to the Base of first transistor and in series to collector of second transistor. Otherwise, too high currents will flow, not good for Leds.
If you have already used this circuit then the IR LEDs are already damaged or atleast <what I would like to call> abused.
It means, they aren't dead, but they produce too little light from too high current.
Try using fresh Leds and use resisters always.
- #40
vk6kro
Science Advisor
- 4,079
- 41
Jbord39 hasn't been around for about a year.
This thread is from 2 years ago and the last circuit does have errors in it.
This is unfortunate as it has had a lot of viewings.
thebeaverwhis:
The circuit was intended to drive a LED on an infra red transmitter, but it might be OK for a motor if the transistors could carry enough current.
However, a motor can draw a lot of current if it is stalled and this could easily destroy a transistor if it wasn't big enough to cope with the current. So, you would be safer using a relay to switch a motor.
You may need to hunt around for a complete circuit for a transmitter and a receiver and a motor driver if you want to make up a complete setup.
Post #5 above gives part of a complete transmit / receive setup.
If your distances are small, you might be able to use a simpler transmitter and a infrared phototransistor as the receiver.
This thread is from 2 years ago and the last circuit does have errors in it.
This is unfortunate as it has had a lot of viewings.
thebeaverwhis:
The circuit was intended to drive a LED on an infra red transmitter, but it might be OK for a motor if the transistors could carry enough current.
However, a motor can draw a lot of current if it is stalled and this could easily destroy a transistor if it wasn't big enough to cope with the current. So, you would be safer using a relay to switch a motor.
You may need to hunt around for a complete circuit for a transmitter and a receiver and a motor driver if you want to make up a complete setup.
Post #5 above gives part of a complete transmit / receive setup.
If your distances are small, you might be able to use a simpler transmitter and a infrared phototransistor as the receiver.
- #41
I_am_learning
- 682
- 16
vk6kro said:
Too bad that I never check dates.
- #42
jbord39
- 74
- 0
I_am_learning said:
I am back!
About the mistakes in the circuit, I had just started designing electronics (I had just started college).
The green LED should be connected to 5V instead of ground on one end.
Also the reason for 5V as opposed to 9V is to prevent changes in the circuit functioning (like oscillation frequency) when the battery voltage drops. It provides a voltage supply 'buffer' of sorts.
And the diodes should have a current limiting resistor. I tried a million times and something is wonderfully broken because with a resistor I can't get 100 mA in each diode. They are abused perhaps but still working just as well (the sender will bounce around a wall before losing power to the receiver).
I will post a receiver circuit soon.
- #43
jbord39
- 74
- 0
Hey an updated (an better) schematic is in the attachments. The tuning pot is used to make sure the output is right around 38kHz. The receiver (output is HIGH with no input and LOW whenever it receives 38kHz, from Radioshack) is hooked up to a 555 timer in monostable mode (this produces a single long output whenever its trigger goes LOW). The output is To BeagleBoard.
Currently the monostable 555 produces an output that is about 1-2 seconds long. If you are running something and need it to stay on for like an hour or more you could change that. You could also modify the monostable 555 to make it more like a flip/flop.
The main problem I had with this circuit is that the device you are turning on needs a constant supply of power just to monitor if it is going to be turned on or off. So for a receiver something plugged into the wall works best as opposed to battery powered.
Currently the monostable 555 produces an output that is about 1-2 seconds long. If you are running something and need it to stay on for like an hour or more you could change that. You could also modify the monostable 555 to make it more like a flip/flop.
The main problem I had with this circuit is that the device you are turning on needs a constant supply of power just to monitor if it is going to be turned on or off. So for a receiver something plugged into the wall works best as opposed to battery powered.
