I am a beginner and I am still not very confident working with current amplification. So I have a 5v source supplying about 1.2 mA, and I need to convert the 1mA into 160 - 180 mA. What are the ways I can achieve that ?? After some research I found that op amps allow us to amplify signals, but I am not sure if that applies to currents as well. Anyways, I would just like to know what you guys think the best way to go about this is.
Thanks in advance for any help !! 
Is this an on-off kind of signal? If so, a simple transistor switch should be sufficient. The 'Beta' (Current Gain) characteristic of the transistor will tell you how much more current the transistor will pass than the current supplied at the Base of the transistor. To switch 180 mA with a 1.2 mA signal you need a Beta of 150.
If it is not an on/off 5V signal then you should probably explain in much greater detail what you want to do.
I am not sure if it is an on-off signal. Basically I am trying to use a bluetooth module connected to the arduino, to open my garage door. I connected a 5v relay, that would basically close the circuit and open the garage doors whenever the bt module receives a signal from my phone. I tested my circuit with an LED and it works well.
Now, the issue is that I would like to power all of this, I thought of using a 9v alkaline battery, but I do not know how long the battery would last before having to replace it. Or I could just power the arduino using a 5v output on the garage controller board. The current coming out of the 5v the garage controller provides is about 1.2mA.
I looked online and found that a 5v relay needs about 90mA, an arduino nano needs 19 mA, and a Bluetooth module needs about 50mA. All of this adds up to about 160 mA.
I am not sure if the 5v output the garage controller provides is an on-off kinf of signal or not. I hope this was enough information. Thanks !
A raw circuit diagram would explain more than thousand words.
I drew this, I hope it makes sense. So the issue is that I need to power the arduino. I can power it with an alkaline battery, but I would need to change it every time it dies. I thought I could connect the arduino nano Vin to the 5v supply on the garage board. But the issue is that it only supplies 1.2 mA. I am not sure how much current this project draws (arduino nano, relay, hc 05 bluetooth module). I assumed that all these components together require about 160 mA (correct me if I am wrong).
So the whole point of the project is to connect the bluetooth module to my phone, send a signal to activate the relay. Activating the relay would connect the 2 wires that act as a switch to open the garage doors.
I hope this was good enough of an explanation. The diagram I attached models this whole procedure.
Thanks !
You need a transistor to drive the relay.
See this instructable for a similar project.
It includes a circuit diagram for the components to drive the relay.
Basically just a transistor, resistor, and a flyback diode.
You could use something like an ESP8266 based WeMos module instead of the Nano and Bluetooth
module. That could give you a nice web based interface where you could do any number of things including the ability to ask additional authentication using buttons, PIN, etc.. on the web page.
All in a very small inexpensive package.
If you google around for "esp8266 garage door opener" you can find several projects.
--- bill
I don't think you can use the garage controller for power. It's not intended to drive anything else, but I'm a little surprised that there's such a tiny current on the 5V line - it sounds like that's a driven output that was off when you measured it. Can you post a picture of it?
wildbill:
I don't think you can use the garage controller for power. It's not intended to drive anything else, but I'm a little surprised that there's such a tiny current on the 5V line - it sounds like that's a driven output that was off when you measured it. Can you post a picture of it?
I agree. If the power is that low (How is it documented? or was it measured? and how?)
That line may be for something else, like a sensor or something.
Some garage controllers do have voltage lugs for accessories.
A photo of the controller would be nice.
Many garage door buttons have a light in them that is driven by the voltage in the wires that connect to the button.
It is possible to siphon off some power off that but likely not much or it triggers the controller to open/close the door.
--- bill
yes the 5v output is for the radio antenna that receives signals from the garage door remote.
You can't get 0.9 Watts (5V * 0.180A) from a source that can only supply 0.006 Watts (5V * 0.0012A). You can't power your Arduino from the "5V Output" of your garage door opener. It was obviously not intended to be a power source.
I'm guessing that your garage door opener, like mine, is plugged into AC power. Just plug in a USB charger and run a USB cable from the charger to the Arduino to power it.
