Electronics > Beginners
Real World Use Of A Function Generator
Doctorandus_P:
Not very long ago I decided to finally buy a Function generator.
I bought the cheapest version of the JDS6600 with a 15MHz bandwidth.
It is one of the tools I should have bought much earlier.
When I was young (30 years ago) a function generator with such specifications was ... expensive, almost non-existant, and then you sort of fall in a pattern of building simple test signal generators for separate projects.
My last serious use of my JDS6600 was for an Inductor tester. I built a circuit on Veroboard with a Fet driver, a beefy N-channel MOSfet, a bank of Elco's and an inductor to test.
For test signals I needed narrow pulses to measure the current through the inductor and other things. There are many variants of power inductor testers:
https://duckduckgo.com/html?q=power+inductor+tester
I simply copied the schematic from the first link:
https://ludens.cl/Electron/lmeter/lmeter.html
Such an inductor tester is a pretty trivial circuit. Most of the components and connections are in the 2 NE555 IC's, which are used as a simple signal generator (Frequency and pulsewidht). Instead of those NE555's I just hooked up my Function generator which saves me some time and also has much more accurate control on the test signal that goes into the MOSfet.
There are many of such test circuits which can be simplified by using your function generator instead of soldering together a custom signal generator.
Another recent quick use of my Function generator is for testing stepper motor drivers. You can easily generate step pulses to test what the maximum motor RPM is with different power supply voltages and loads.
And that's only a small part of the PWM signal generator part of this thing.
In the analog domain it can also do much more than I have used yet.
With the 2 syncronised outputs of the JDS6600, Lissajous figures become so trivially easy it's boring, but if you want you can add some drift by changing one of the sine's in steps of 0.01Hz.
One of the classic first transistor circuits when you start with electronics is a single transistor amplifier with a few resistors. To test this, you need an input signal and a function generator is an easy source for test signals.
What you get for around EUR 60 is amazing, but in this price range it's got some limits.
The power supply adapter is garbage. Throw it away and use a decent adapter, or put a simple block transformer + LM7805 in the thing itself. Plenty of room.
On low amplitude it gets a bit noisy. The signal is generated by a 12-bit ladder DAC on the output of an FPGA.
If your're into audio you can use some (decent) extra USB audio adapter and modify it a bit to get a pretty decent / low noise audio source. There are loads of programs available to generate live audio signals (Sine, triangular, sweep, whatever). You can add some switches and pot meters for easily accesable adjustments for volume AC/DC coupling and offset. But I'd rather have my JDS6600 for almost any signal (When the low-noise is not a big point).
LapTop006:
As others have said, it's not one of the pieces of kit you buy first off.
A year ago I had none, now I have three, two quite specialised & handy in their niches, but otherwise not very useful, and a general function gen (in my case all three are from Stanford Research).
If you're purely doing microcontroller work they might not get much use as anything other than an occasional clock, but if you're doing analog or RF they're really handy.
Rerouter:
I should point out most "Function Generators" these days are actually Arbitrary Waveform Generators, Now what difference does that make? well it lets you abuse it in fun ways.
For digital, your trying to reverse engineer a bus, so do you spend a day building something to playback a protocol message at an exact moment, or load the pattern into a AWG and use its trigger input, and have it respond in nanoseconds, Equally, how does the device behave if I slow things down or speed it up, what if I slice out the dead time, so its 100% protocol load, what amplitudes are valid, and the best one, what unspeakable bugs appear after 24 hours of noise in the correct frequency and amplitude range, I've used mine for playback attacks on some fun things, (send a small set of messages back and poke at what changes each time)
Equally with multiple outputs, its easy to quickly roll your own PSK / ASK / FSK etc encoding, some can even use the trigger to switch this internally, so again, instead of needing to program up for it, just feeding a TTL converter to its input trigger gives you a way to generate a silly amount of protocols.
Wimberleytech:
--- Quote ---...
What you get for around EUR 60 is amazing, but in this price range it's got some limits.
The power supply adapter is garbage. Throw it away and use a decent adapter, or put a simple block transformer + LM7805 in the thing itself. Plenty of room.
On low amplitude it gets a bit noisy. The signal is generated by a 12-bit ladder DAC on the output of an FPGA.
...
--- End quote ---
You have damn near convinced me that I should have one on my bench!!
bd139:
I use my function generator all the time. 90% of what I do is playing with signal processing of some sort in the audio and RF frequency domains.
Without a wide range signal source it's a total pain in the arse doing a whole class of testing. Even fixing basic things tends to require a signal source.
Currently have an HP 33120A AWG but have had a couple of analogue ones and a Rigol one before that.
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