Okay, So I am creating an actual phone for disabled people with the Arduino GSM shield. Basically though there is interference. So for starters this whole project is powered off of 24 volts from an electric wheelchair's batteries. I have a 5 volt pololu regulator for sensors, the Arduino and the GSM shield. I also have a DROK 24 volt to 12 volt regulator from amazon for the speakers amplifier and some LEDs. I noticed when ever the GSM shield makes a call there is a LOT of background noise in the circuit which results in the speaker which is connected to a small amplifier to produce the standard GSM interference sound. I have tried shielding portions of the electronics with no luck. However, I discovered that if I take the GSM shield off of the Arduino and power it off of a different source such as a battery there is no noise what so ever. What can I do to keep only one power source while avoiding the interference. All of the electronics are common grounded and if I power the GSM shield off of another regulator from the wheelchair batteries it still produces the noise. What can this be?
Thank you everyone!!
EDIT: there was a missing ground on the audio lines, fixed it and put a ground loop isolator in. Static vanished.
How about the "Common Ground"?? The best point is probably the negative terminal of the battery, or where the negative terminal of the battery is connected to the wheelchair motor or frame. Separate ground wires from the different devices to that point.
Other:
Does the sound vary with the volume control of the speakers?
Where is the GSM antenna relative to the audio equipment?
Do you get the same noise when making a GSM cell call on a handheld phone close to the electronics?
(Trying to diagnose common mode noise, VS picked up Radio Frequency energy vs ???)
I think the GSM Shield needs it's own battery.
I don't see how you can power a GSM shield off a switching regulator and not have noise without adding all kinds of capacitors for filtering and decoupling.
Put 1000uF on the GSM shield power input and 0.1 uF on the arduino 5 V Experiment putting different value caps on power inputs and outputs to see if ANYTHING effects the "noise" level from the speaker. I doubt anything will work as well as running the GSM off a battery.
Looking at your picture how do you figure that will work you don't stick your cellphone inside it's power supply do you it has a cord you have it right next to the power supply you'd have isolated the power supply with shielding. Your GSM is next to basily a transmitter called a switching supply. And you have it warped in ant's called wires.
You need to put the entire audio amplifier inside a shielded box, and decouple all the wires
going into the box .
GSM uses TDMA so when transmitting its basically a hi power AM transmitter
right next to a low level audio amplifier.
Other solution is to not use GSM and use 3G which doesnt have the interferance problem.
Very poor design technique. Designing products that involve RF requiress some basic knowledge of RF design principles. To say it violates all common sense guidelines about RF would be an understatement. Back to the drawing board.
lead project boxes come in some small sizez too. I think Halted Specialties in Santa Clara, CA, USA has a good selection.
You should change your post title to :
"How NOT to Design a Science Project" ( is this your Senior Project ?)
FYI, circuit layout & shielding block diagram is discussed in the FIRST Design Review meetings, not the LAST ones....
In case anyone was wondering the audio lines going to the speaker amplifier were missing the ground connection (bad audio jack). This caused the audio ground to go through the GSM shield and all the way around into the amp. I replaced the audio jack and put a ground loop idolator in the middle. Problem solved. current designed worked. No issues what so ever.
In case anyone was wondering the audio lines going to the speaker amplifier were missing the ground connection (bad audio jack). This caused the audio ground to go through the GSM shield and all the way around into the amp. I replaced the audio jack and put a ground loop idolator in the middle. Problem solved. current designed worked. No issues what so ever.
Thanks for the SITREP update ("SITREP" : Milspeak for "SITUATION REPORT")