Hi,
If i connect a sim900 power pins to a step down, the module sim900 will power on without problems.
If i connect the same sim900 module to the same step down, but i use an breadboard, the sim900 module power go down.
It's sounds like there are disturbs between holds.
Sorry for my english, i hope i've been clear.
Thank's
Show us a photograph and a diagram of your setup.
Just remember bread board is crap. Also t is limited in the amount of current it can handle, anything over 200 mA and you should be soldering on strip board.
I had a breadboard with bad connectors. Try moving your device to different holes and see if the problem persists.
Grumpy_Mike:
Just remember bread board is crap. Also t is limited in the amount of current it can handle, anything over 200 mA and you should be soldering on strip board.
While I still heavily use them.. for keeping all sorts of 'circuits' prototyped and available when I need them..
I agree with what GM says..
you can definitely get varying quality of breadboards.. (some with crap 'connections' .. some with crap 'holes'..etc)
As far as the current issue.. I always thought it was more like .5A (500mA)...
(as I have had like 20+ leds @ 20mA each in testing)... so I'll have to keep the 200mA limit in mind myself!)
I also feel bad for anyone that thinks a breadboard is good for a final design instead to transferring to a soldered solution.
So many things are going to go wrong.
I don't know anyone who thinks that. Breadboards are very useful for prototyping and experimenting.
The breadboard may also have an internal short as well. I just got one with a faulty power rail, which could cause your symptoms.
Grumpy_Mike:
Just remember bread board is crap. Also t is limited in the amount of current it can handle, anything over 200 mA and you should be soldering on strip board.
Yes, that is why ,i didn't think about it.
I have one other question.....
What do you think about that: when i use an 9v battery 200mha If i connect my sim900 to step down it works... if add two wire, free in the air, to power + and - sim900 goes down when it try to power on.
But if i use a power supply it doesn't happend.
is it happening becouse the 9v battery is undersize?
Thank's
I didn't quite follow the wiring arrangement you described but yes those 9V rectangular batteries are very poor at delivering much current.
It is alright saying it is 200 mAH but that doesn't mean it will deliver 200mA for one hour. More likely it will deliver 50mA for 4 hours though. Those figures are just made up but the point is that with these batteries the lower current you draw the larger the mAH figure you can claim.
pwillard:
I also feel bad for anyone that thinks a breadboard is good for a final design instead to transferring to a soldered solution.So many things are going to go wrong.
Hi,
Be happy 
it's not a final work... it's a test.
Usually i make negative pcb with a good quality only when i'm sure that's all right.
I feel bad for those who don't breadboard first, and have to cut traces and add jumpers later.
<<<<<< this guy
I did a system in bread board and it was running quiet well for more than a year, it looks very ugly but served me without any issues. Recently I moved to a soldered solution by making a PCB.
Bread board solution based on Raspberry pi
New solution based on a PCB based on Arduino
Working on the next version of the board. The above system controls my Aeroponic garden at home.
I do all the prototypes in a breadboard before I go for a PCB.
