Bit of an electronic newb here, so try to be gentle. I'm doing a university research project on MFA, so I decided to build an implementation of a system I designed as a PoC. Anyway...things I have:
Intel Galileo (PoC is written in Python, easier to migrate)
12V 4A Regulated Power Supply for door strike and and keypad
The general idea (without the code) is to use the the bluetooth module (remotely from android) to send a dW to a pin on the Arduino, allowing the transistor to output 12V for the keypad, allowing the keypad to function. A correct pass on the keypad allows the lock to open.
My issue (right now):
I can not get the transistor to output 12V. I've followed all sorts of tutorials and I can not get it to work. Does this sound like a feasible project? Is there something I'm missing? You can see that I am using dual power supplies. If I measure + from the 12V power supply and - coming from the middle pin (http://www.adafruit.com/datasheets/TIP120.pdf) after the base has been set to high (from the arduino, which is powered by the 5V), I should see 12V on my multimeter, right?
This is been the main tutorial I've been following to get it off the ground. Is there something wrong with it?
Draw a schematic and take a photo of it with your cell phone and post it. There is no reason why you should be having this problem. It is probably wired wrong. Based on this:
allowing the transistor to output 12V for the keypad, allowing the keypad to function.
Your wording sounds suspicious . It sounds like you're trying to SOURCE 12V instead of SINK it.
Post the schematic so we can check it out.
raschemmel:
Draw a schematic and take a photo of it with your cell phone and post it. There is no reason why you should be having this problem. It is probably wired wrong. Based on this:
allowing the transistor to output 12V for the keypad, allowing the keypad to function.
Your wording sounds suspicious . It sounds like you're trying to SOURCE 12V instead of SINK it.
Post the schematic so we can check it out.
Here's what I have. There is a HC-05 module on the 5V rail which is also wired up (I'm bad with Fritzing, sorry). Instead of the point I described (mystery part on the drawing), there is a keypad with a 12V in/out on it that leads to a door strike; however, I can't get the 12V to the point when I write HIGH or LOW to pin 9.
Remove the TIP120 from the breadboard.
Put your meter on DIODE scale.
Put the red (+) lead on pin 1 (base)
Put the blk (-) lead on pin-3 (emitter)
What does the meter read ?
Move the blk (-) lead to pin-2 (collector) while keeping red (+) lead on pin-1 (base)
What does the meter read ?
What is your +12V voltage source (a walwart or what ?)
Put the meter on OHMs scale
Measure the coil resistance of the door lock
What is it ?
Don't do anything with the circuit till you hear back from me after you answer the above .
See attached schematic of how your circuit should be wired.
I'm missing? You can see that I am using dual power supplies. If I measure + from the 12V power supply and - coming from the middle pin (http://www.adafruit.com/datasheets/TIP120.pdf) after the base has been set to high (from the arduino, which is powered by the 5V), I should see 12V on my multimeter, right?
Wrong. If you make d9 HIGH, the transistor should turn ON. When it turns ON, it will become a SHORT (as far as you are concerned. Actually there will be a small voltage drop across collector and emitter but basically you should see +12V when the transistor is OFF and almost ZERO when it is ON. You should NOT be looking for +12V on the collector of the transistor when it is on. You should concern yourself with whether or not it is turning on. Which at this point , it is hard to tell. You have not said whether or not the door lock is working (I don't know what door "STRIKE" is , so let's just say LOCK ON /LOCK OFF ok?) . Instead of telling us if the lock is turning on or off your are concerned about see 12V on the collector of the transistor when it is on which will NEVER HAPPEN, so forget that idea and let's move on.
