i have everything working just fine and dandy on my uno. But I want to use the receiver with an atmega8 on a breadboard. I uploaded the sketch and it works fine. Then I tried unplugging it from the usb and using a 6v power supply (4 AA battery pack). Now it doesn't work. Then I tried 2 2032 coin cell batteries. Then it worked again! I assume it has something to do with the voltage or current, but frankly, i have a really bad grasp of all of that. The specs for the receiver say it uses 5v, but then why do the coin cells work? I tried different resistors between the battery and the VCC pin on the receiver, but no luck. (and yes, the AA batteries were fresh and working).
But after that, I take it out and am left with a very simple circuit.
Like I said, it works with the coin cell batteries. I had it sitting on one side of the room, by itself, blinking every time it received a message from the transmitter on the other side of the room. I just don't want to rely on those small (and expensive) batteries for this project, and I'd like to understand what's happening so I can apply the knowledge to future endeavors for ever and ever.
My guess is that the coin cells have a lower internal resistance than the AA batteries, and thus can react to transients much faster, compensating for your lack of decoupling capacitors.
Majenko: can you explain decoupling caps? What capacitors should i use? Where do I put them?
Perhof: I use a pull-up resistor on the reset pin when I'm connected tot he usb module for uploading code. Why would I need it during regular, stand-alone use, and how would it help me problem?
ok. What resistor should i use and where should i put it (from reset to...)?
Just to be clear- this simple setup has worked for me for other things- with the AA batteries, and no caps or resistors.
Which leads me to assume that the problem is something specific to using the rf receiver.
The problem is the 433 Mhz receiver, they are very critical on supply voltage.
They need 5V plus or minus 0.5 V.
They wont work on 6V.
The reason most likley that the coin cells work, is that they arnt designed for delivering much current, so its likley
the current the Mega8 is pulling is causing the cell voltage to droop a bit.
If you want they system to be reliable its best to run the receiver off 5 V regulated.
thedovid:
Ok, so I can use a 9v battery then, right?
Yes... kind of.
The little PP3 9V batteries don't last long though, as they have very little capacity, and with a linear regulator they last even less time.
If you want it to last a while you should be looking into other power sources, like Lithium Ion / Lithium Polymer, and switching (buck / boost) regulators.
A typical PP3 has only 565 mAh, whereas your normal AA battery has 1800-2600 mAh.
Just put a diode coming from the positive side of the battery it will drop you down enough to make
the receiver work
4 AAA one diode makes 5.3 volts and will keep you from hooking the battery's wrong XD