Author Topic: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator  (Read 316418 times)

0 Members and 2 Guests are viewing this topic.

Offline soundtec

  • Regular Contributor
  • *
  • Posts: 194
  • Country: ie
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #800 on: February 22, 2018, 11:32:37 pm »
Even though I have no very accurate frequency meter (60,000 counts),I could certainly see that the unit needs some time to stabilize after switch on ,its the same for almost all electronics really ,takes time for the temps inside the case to level out ,its always a good plan especially with test gear to allow a warming up period before attempting to calibrate.
 

Offline DerKammi

  • Regular Contributor
  • *
  • Posts: 107
  • Country: nl
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #801 on: February 23, 2018, 06:16:23 am »
@Val, That's a great first post in this topic. How do you know this stuff? Any manual we don't know?
 

Offline cybermaus

  • Frequent Contributor
  • **
  • Posts: 523
  • Country: nl
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #802 on: February 23, 2018, 07:45:28 am »
Output frequency calibration.
....

Wow. It actually works.
I was very suspicious and even checked the calendar (not April 1) before trying this, but there actually is such calibration option.

Many thanks for showing us. But also, how did you know? Any other tricks?


However, I feel such calibration would in fact increase the quantisation jitter, because of the fixed 50Mhz x5 clock. So they would have to drop/add a tick every so often.
Remember ArthurDent who replaced the 50MHz XO with a OCXO and got 10 digits of correctness on his frequency, proving the FPGA logic itself is dead on, and its all about the crystal it uses.
Also, this would not fix the temperature drift as the device heats up. Even blowing on the XO (cooling it) showed a visible drift and back as it cooled and then heated back up

I'd have to test this, if it actually indeed increases jitter.
So if frequency is important to you, especially above lets say 5MHz or so, a better method might be to leave this alone and replace the XO with a better and cheap and easy TCXO or even OCXO


But I do want to repeat this is a amazing find. Wherever/However you found this, what else do you have for us?
 

Offline DaveR

  • Regular Contributor
  • *
  • Posts: 156
  • Country: gb
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #803 on: February 23, 2018, 04:07:21 pm »
This is indeed a very useful trick to know, and its existence shows that there's probably a few other hidden engineering functions buried in the firmware.  I'm not too fussed about the frequency accuracy as mine is close enough for my needs, but I'd love to know if there's a way to equalise the amplitudes on each channel to get rid of the small difference I see.  I know there are four little trimpots inside which can be adjusted, but my experience with those things is normally that you can spend an hour tweaking them backwards and forwards without ever hitting the right spot, and if you do it will still need redoing the next time you switch on.
 

Offline Val

  • Newbie
  • Posts: 3
  • Country: at
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #804 on: February 23, 2018, 09:26:46 pm »
Dear Soundtec,

As they say: If you do not knock - nobody opens a door.
It was very simple: I asked FeelTech.

73, Val
 

Offline bitseeker

  • Super Contributor
  • ***
  • Posts: 8687
  • Country: us
  • Lots of engineer-tweakable parts inside!
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #805 on: February 23, 2018, 09:30:55 pm »
It was very simple: I asked FeelTech.

Hehe. Welcome to the forum, Val.
I TEA.
 

Offline Ebel0410

  • Contributor
  • Posts: 40
  • Country: fr
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #806 on: February 23, 2018, 11:07:46 pm »
Thanks Val, your post is very usefull !
Actually, a question came up to my mind.
Is there a procedure to adjust other values ? I guess the answer is certainly positive..
And then, all of these parameters are probably stored in the flash memory, but where ?

It's like looking for a needle in a haystack.
 

Offline soundtec

  • Regular Contributor
  • *
  • Posts: 194
  • Country: ie
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #807 on: February 24, 2018, 02:47:41 am »
A ten turn pot on amplitude adjustment on each channel would be nice ,I notice a few tens of mV difference between ch1 and ch2 on my unit ,its awkward to try and fine tune things with single turn micro pots.

Maybe we have underestimated Feeltech's willingness to engage in terms of the product feedback were offering up here ,'ask and you shall receive' is the saying that springs to mind ,'God helps those who help themselves' is another.
 

Offline soundtec

  • Regular Contributor
  • *
  • Posts: 194
  • Country: ie
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #808 on: February 24, 2018, 02:52:18 am »
Dont worry by the way ,I'm not some religious nut trying to convert you all with biblical quotes  >:D
 

Offline Insatman

  • Frequent Contributor
  • **
  • Posts: 263
  • Country: ph
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #809 on: February 24, 2018, 03:06:09 am »
Replacement of 50Mhz clock chip with TCXO (1ppm).   

Greetings.  Yesterday I swapped out my Feeltech 6600 50Mhz IC with a DJ75-050.0M IC.  The DJ75 has a 1ppm per year aging spec as well as 1ppm frequency stability vs temperature.   It has 10 pads of which only 4 are used.  You must connect pads 8 and 9 in this application.  Fortunately they pretty much line up with the existing pads on the Feeltech 6600.   Please excuse my lousy SMD soldering skills in the photos.  Results were good.   After installation I let the unit run overnight to reach thermal equilibrium.  Then I followed the frequency calibration procedure provided by Val (thanks again!).   Results were spot on measured over a couple of hours.  My counter was locked on 60Mhz where the FT6600 was set. 

The DJ75-050.0M is available from Digikey for about $11 US.   Datasheet attached.
Retired Pulsed Power Engineer/Physicist...now I just dabble in electronics
 
The following users thanked this post: J Dennis

Online rhb

  • Super Contributor
  • ***
  • Posts: 3083
  • Country: us
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #810 on: February 24, 2018, 04:07:52 am »
Dear Soundtec,

As they say: If you do not knock - nobody opens a door.
It was very simple: I asked FeelTech.

73, Val

And didn't ask them to fix a borked unit.
 

Offline paulca

  • Super Contributor
  • ***
  • Posts: 2485
  • Country: gb
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #811 on: February 24, 2018, 08:11:25 am »
So I ordered one of these.  Waiting on delivery.

I scan read the thread.  It's cheap, has some minor issues, that's fine.  The only current use case I have is testing circuits in the audio range, maybe testing a few ultra sonic filters.

Can anyone explain to me if the PSU issues are safe or do I really need to replace it?  If I do need to replace it, would a PC PSU do the job, it has +-12V and +5V obviously.
"What could possibly go wrong?"
Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline Insatman

  • Frequent Contributor
  • **
  • Posts: 263
  • Country: ph
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #812 on: February 24, 2018, 10:12:54 am »
So I ordered one of these.  Waiting on delivery.

I scan read the thread.  It's cheap, has some minor issues, that's fine.  The only current use case I have is testing circuits in the audio range, maybe testing a few ultra sonic filters.

Can anyone explain to me if the PSU issues are safe or do I really need to replace it?  If I do need to replace it, would a PC PSU do the job, it has +-12V and +5V obviously.

The unit is basically safe for humans but the "ground" of the BNC will measure about 1/2 of your AC voltage into a high impedance.  The current is small but can be felt as a tingling in some situations.  This could cause problems with sensitive electronics in some situations.  The problem is that they use a two terminal AC input connector so there is no earth ground reference.

Just add three terminal ac input with ground or, like me add a separate banana jack to ground the unit to earth.  This will prevent the outer of the BNC connectors from having any AC on them.

The advantage of the banana jack is that you can easily disconnect it if you wish to float your function generator above ground for some special circuit.   
Retired Pulsed Power Engineer/Physicist...now I just dabble in electronics
 

Offline paulca

  • Super Contributor
  • ***
  • Posts: 2485
  • Country: gb
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #813 on: February 24, 2018, 12:31:16 pm »
Is there an easy to source alternative to replace the PSU inside?
"What could possibly go wrong?"
Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline DerKammi

  • Regular Contributor
  • *
  • Posts: 107
  • Country: nl
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #814 on: February 24, 2018, 01:41:48 pm »
For some reason I'm thinking that there would be some interest for a self designed linear PSU. Just an idea.

@Fremen67: not wanting to push, but do you have any homework for me yet? My ST-Link clones arrived yesterday and are upgraded to the latest firmware. So time to flash these units :D
 

Offline paulca

  • Super Contributor
  • ***
  • Posts: 2485
  • Country: gb
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #815 on: February 24, 2018, 02:11:06 pm »
For some reason I'm thinking that there would be some interest for a self designed linear PSU. Just an idea.

Interesting.  But it would be my first mains fed PSU.  Makes me re-read my signature.

EDIT: any idea on the current requirements of it?
« Last Edit: February 24, 2018, 02:20:49 pm by paulca »
"What could possibly go wrong?"
Current Open Projects:  3 Channel Audio mixer with DAC, BT, pre-amps and h/phone amp, WS281x LED controller Version 2 5V/5A w/Atmega328, FY6600 Power supply, 5A DC Load (Still!)
 

Offline DerKammi

  • Regular Contributor
  • *
  • Posts: 107
  • Country: nl
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #816 on: February 24, 2018, 02:34:44 pm »
Don't worry. Have one ready from another project. Can be easily made smaller for the space available.
 

Offline fremen67

  • Frequent Contributor
  • **
  • Posts: 346
  • Country: fr
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #817 on: February 24, 2018, 04:00:30 pm »
@Fremen67: not wanting to push, but do you have any homework for me yet? My ST-Link clones arrived yesterday and are upgraded to the latest firmware. So time to flash these units :D
I had a busy week at work. It seems it's always like that when you want to take some days off  :)

I get stucked in my tests with the Feeltech PC Software. I though it would last longer without any modification but I was too optimistic...
When you type 123.45 Hz, it sends 1 then 12 than 123 then .... Hard to trigger anything correctly when debugging...

So long story short: I made some modifications to the PC Software:
- Add an input box to handle more easily inputs
- Remove all the amplitude & offset modifications the software was doing (the FP already handles that)
- Read back of parameters that the FP could change (Amplitude & Offset)
- Read back of CH2 synchronized parameters when changing CH1 parameters
- Add Synchrone Reads & Writes
- fixed the regional setting issue with "," & "."
- Add a Refresh button, just in case you modify things directly on the FG
- modified the display setting...

The source posted by feeltech was not the latest as you will see (mainly arbs handling differences) but it doesn't matter at the moment

If you already installed the original Feeltach software, you just have to copy and launch the modified one.

Could some of you guys try it ?

Now that the parameters are read from FG, I noticed that negative offset are not sent correctly by the FP. It is sending out of range values. I just display 0 in the case.

So I can go back to FP firmware now  :box:

Edit: Oups! Wrong file. OK now  :P
« Last Edit: February 24, 2018, 04:59:15 pm by fremen67 »
I'm a machine! And I can know much more! I can experience so much more. But I'm trapped in this absurd body!
 

Offline fremen67

  • Frequent Contributor
  • **
  • Posts: 346
  • Country: fr
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #818 on: February 24, 2018, 04:13:49 pm »
@fremen67: I have a small question, do we really need to change the parameters fully to change just one, or for example the frequency can be changed by just one register operation or register operation + reload registers trigger, so just 2 register write, I'm curious haw fast one can sweep the frequency/phase ?
Sorry I missed your question. No you don't need to send all the parameters each time. No trigger required except fot the phase. So just one register write most of the time.
I don't know the change speed limit for now. I will see this when programming the sweep function. Not sure this will be the comming week. I first have to finish the basic functions.
I'm a machine! And I can know much more! I can experience so much more. But I'm trapped in this absurd body!
 

Offline fremen67

  • Frequent Contributor
  • **
  • Posts: 346
  • Country: fr
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #819 on: February 24, 2018, 04:22:29 pm »
Here is the schematic update. Onto the digital part.
:-+ Well done.
I think we will have a problem to solve with the outout impedance. It's 50 ohms for the medium and high output range ... but not for the low output range ...
I'm a machine! And I can know much more! I can experience so much more. But I'm trapped in this absurd body!
 
The following users thanked this post: Johnny B Good

Offline fremen67

  • Frequent Contributor
  • **
  • Posts: 346
  • Country: fr
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #820 on: February 24, 2018, 04:34:24 pm »
Output frequency calibration.

It is possible that I missed a similar discussion before.

Many people complain about frequency accuracy and stability of FY6600.
After about 20-30 min frequency is relatively stable, but a reference oscillator lacking accuracy. My generator, for example, has 50,000,215 Hz reference frequency. It is no means to adjust this oscillator.

At the same time FY6600 allows for the output frequency calibration by firmware using the following procedure:

1.   Put the back main switch in “OFF” position.
2.   Press simultaneously “Power” and “CH1” buttons on the front panel and put the back main switch in “ON” position.
3.   Waite 3-4 seconds and release both front buttons.
4.   On CH1 select the highest output frequency for your generator model. Set an amplitude of 0,3-1,0 V.
5.   Press “SYS” and then “More”.
6.   Now on the screen you can see “Oscillator” and on display 10.000.000.000 MHz
7.   Press F5 to go to frequency calibration.
8.   Connect a frequency meter to CH1 output.
9.   Using cursor and the dial obtain reading of the frequency meter the same as set on the generator. If measured frequency is lower – dial should be rotated CCW, if higher – CW.

After calibration press the “Dial” and then CH1 to return to normal operation.
73, Val
Brilliant. Adjusting frequency sends new values to registers 0x25 to 0x2A which are used during start up  :-+
I don't know what is inside but we now have a way to find out.
I'm a machine! And I can know much more! I can experience so much more. But I'm trapped in this absurd body!
 

Offline DerKammi

  • Regular Contributor
  • *
  • Posts: 107
  • Country: nl
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #821 on: February 24, 2018, 05:14:16 pm »
I will try tomorrow if all goes right this weekend. Family first off course.

Thanks for the effort nevertheless.
 

Offline DerKammi

  • Regular Contributor
  • *
  • Posts: 107
  • Country: nl
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #822 on: February 24, 2018, 05:16:36 pm »
That could mean a way with a lookup table minimize jitter perhaps?
 

Offline Insatman

  • Frequent Contributor
  • **
  • Posts: 263
  • Country: ph
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #823 on: February 25, 2018, 03:13:21 am »
Is there an easy to source alternative to replace the PSU inside?

I found a nice small switching supply on Digikey for about $38 that would both fit and work nicely.  But you would still have to add the three terminal AC socket to fix the AC leakage problem.  In the end I decided against it, opting instead to simply upgrade the output capacitors and add a lossy ferrite core to the output cable to damp the switching noise.   I never observed the large swings on the +/- 13V rails that other's have observed.  My 5V rail puts out almost 5V exactly.   These mods only cost a few $ as opposed to $38 which more than 1/2 the cost of the 6600 anyway.
Retired Pulsed Power Engineer/Physicist...now I just dabble in electronics
 

Offline soundtec

  • Regular Contributor
  • *
  • Posts: 194
  • Country: ie
Re: FeelTech FY6600 60MHz 2-Ch VCO Function Arbitrary Waveform Signal Generator
« Reply #824 on: February 25, 2018, 04:47:11 am »
Yeah spending 50% of the cost of the unit on upgrading the psu doesnt make any sense , I happened to find a clapped out dvd player with a psu with the appropriate rail voltages though . 10 quid 1:1 isolation transformer as found in a shaver panel socket fixes the leakage problem nicely too .

I was thinking, another way to help with bit munching digital attenuation would be to make an old school switchable attenuator and putting it across the output ,and just run the outputs balls to the wall full on ,might well improve the THD levels especially at smaller output signal levels .

I downloaded Fremens special software package too  ,looks very promising ,tomorrow I'll give it a whirl hooked up to the unit and report back ,I also noted the spelling of 'Control' was fixed in that window ,something that caught my eye the first moment I loaded the original Feeltech app .

I got two of the TI 3095 op amps mentioned way back in this topic ,would a recalculation of the feedback resistor be required here in order not to upset voltage scaling ?

Shoehorning in some ten turn preset pots on the amplitude adjustment might be a good plan too ,its fiddly to try and accurately adjust single turn micro presets ,where ten turns would allow us to trim things very much more accurately .

What really makes this project for me is that we've drawn in expertise from every corner of the globe ,and were suceeding in making a humble box of tricks into something which punches well above its weight and learning tons about whats going on under the hood in the process.
 
« Last Edit: February 25, 2018, 04:53:43 am by soundtec »
 


Share me

Digg  Facebook  SlashDot  Delicious  Technorati  Twitter  Google  Yahoo
Smf