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Function Generator App for Smart Phone (What jack/cable to use)

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mhs2xs:
I've installed FuncGen on my Android based phone (Samsung Galaxy S). What's the best way to get from the 1/8" TRS female (phones jack) to what I'd need (probes and/or clips) for circuit testing? Can I use a TRS male and solder both the Tip and Ring to the positive probe/clip and the sleeve to the ground?

Your help is much appreciated.

Cheers!
Mitchell

alm:
I would first check the output with a scope or DMM (on the phone set frequency to 50 or 60 Hz and the meter on ACV) to see which of the channels it uses, I wouldn't just short them. Maybe it can use both for dual channel operation?

I would make a headphone plug to female BNC connector (you're unlikely to find them commercially, I think), then you can use standard BNC cables (eg. BNC to grabber hooks). You could also directly attach clips/probes, in that case you would indeed use sleeve for ground and one of the others (see above) for signal.

Some cheap toys like the DSO Nano also use headphone jacks I believe, you may be able to use one of their cables.

mhs2xs:
Excellent. That's what I need to know. I tried to search for a "pocket function generator" to see what was out there but none of the things I found indicated, or even pictured, the cable.

Edit: Yes, the DSO Nano uses a 3.5mm audio jack for the probes. Good call....Thanks again.

the_raptor:
The DSO nano probes are pretty crap (I own one). You could easily knock up your own of the same quality.

They aren't custom with nice strain relief or anything, and will probably kill you if you touch high voltage with them.

However some people do sell audio jack to BNC connectors for the DSO Nano market, those are probably worth the money.

saturation:
Just some thoughts on this approach.

TRS jacks are made for audio applications.  One needs the right sized minijack to alligators and you are set.



Putting better clips, i.e., BNC, shielded cables etc., will unlikely be meaningful unless you can output MHz from this in a quality worth maintaining its fidelity, which will require access direct to the PCB, in which case interesting problems can occur if it doesn't work out.  So, alligators are good enough.

The output of amps to TRS jacks are typically 8 ohms, most electronics equipment is at least 50 ohms, so be aware the impedance mismatch.  Also the output voltage was made to drive mini-earphones or a preamp input, not that required for projects, so beware overloading the output.

Insure the output is AC coupled, so no DC can inadvertently enter via the output jack.  Phones are typically low power/low voltage logic, and may not take kindly to 5V.

If phone gets damaged by misadventure in electronics, a non-contract Galaxy S replacement is ~$500.  If a phone is insured make sure the insurer can't find out its been tampered with.   Lastly, consider the quality of the Android app output, is damaging it worth the risk? Or should one get a function generator kit for < $30, $50 assembled [ Elenco] ?



Some thought for safer experimenting, enjoy!  :D


--- Quote from: mhs2xs on February 11, 2011, 03:04:46 pm ---I've installed FuncGen on my Android based phone (Samsung Galaxy S). What's the best way to get from the 1/8" TRS female (phones jack) to what I'd need (probes and/or clips) for circuit testing? Can I use a TRS male and solder both the Tip and Ring to the positive probe/clip and the sleeve to the ground?

Your help is much appreciated.

Cheers!
Mitchell

--- End quote ---

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