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 Forum index » DIY Hardware and Software » Microcontrollers and Programmable Logic
PIC-based fraktal synth
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catweazle



Joined: Feb 25, 2008
Posts: 28
Location: germany
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PostPosted: Sun Jul 13, 2008 5:17 am    Post subject: Reply with quote  Mark this post and the followings unread

of course,
the circuit itself (PIC) needs 5V, using a 7805 voltage regulator
you can power it with up to 35V.
But the 7805 can get very hot, it's better to use a
"Low Drop" Voltage regulator like LP2954 or something, just google "LDO".
The ldo's don't waste power like the 7805 - they are common and cheap.
You can also use 3x1.5V battery cells.
The PIC itself can be powered directly between 4..7.5 Volts.
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oootini



Joined: Oct 15, 2007
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PostPosted: Sun Jul 13, 2008 6:41 am    Post subject: Reply with quote  Mark this post and the followings unread

cool. i'll use the 9v clip so. thanks again!
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Blue Hell
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Joined: Apr 03, 2004
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PostPosted: Sun Jul 13, 2008 7:53 am    Post subject: Reply with quote  Mark this post and the followings unread

catweazle wrote:
it's better to use a "Low Drop" Voltage regulator like LP2954


As an LDO regulator is a linear device just like the 7805 it still is the product of the actual voltage over the regulator and the actual current through it which has to be dissipated as heat. It will not make the voltage drop go away or reduce the current.

An LDO is useful when the voltage to be regulated is not much lower than the ingoing voltage, an 7805 needs a couple of volts to be able to regulate it's output, the example LDO given above seems to be happy with just 0.8 V.

When you want less heat and still have a considerable amount of voltage over the regulator a switcher is the way to go, but there are possible constructional issues and issues for audio circuits with those.

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oootini



Joined: Oct 15, 2007
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Location: ireland

PostPosted: Sun Jul 13, 2008 10:24 am    Post subject: Reply with quote  Mark this post and the followings unread

crap. it doesn't work. Sad

it turns on and i get a constant low ringing sound that isn't affected by and of the pots/ or switches. gonnna have to go back and re-check everything...

is it possible that the constant sound which remains unaffected by the pot's indicates a really obvious problem?
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State Machine
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Joined: Apr 17, 2006
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PostPosted: Sun Jul 13, 2008 1:48 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
When you want less heat and still have a considerable amount of voltage over the regulator a switcher is the way to go, but there are possible constructional issues and issues for audio circuits with those.



Sometimes if I have a linear regulator that will have a large (Vin-Vout) and thus dissipates a great amount of power, I first find out if I can use a suitable heat sink and use thermal compound. If I can't, I resort to pre-regulating the prime input DC to a more suitable (lower) voltage for input to the second regulator. This method allows two regulators to share the power dissipation and each won't get quite as hot.

I am in total agreement with Mr. Hell, an LDO regulator will not help in this situation. They are normally used in situations when the designer wants to squeeze every millivolt out of a source voltage before the regulator drops out. LDO's generally consume lower current then the older 78XX series and are often used in battery operated circuits that need every volt out of their battery.

With this, many on the forum may want to explore other types of regulators for theor circuits. Battery operated ones in particular. There are so many that are much better than the 78XX series with much better AC line rejection and protective circuits. Take a peek at Linear Technology and National Semiconductor sometime. There is life beyond the 78XX Wink


Bill
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State Machine
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PostPosted: Sun Jul 13, 2008 2:00 pm    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
crap. it doesn't work.


Pull that MCU and check all your voltages ......... Normally if you have a new circuit and have the IC's in sockets, it is prudent to power it up without the IC's and check the power and ground ........ Hopefully it's just a wiring error with no consequence Wink

If your voltages are not right and you did power it up with the MCU in as yo indicated, it may be damaged. If you correct things that were wrong, then reinsert the chips and the circuit still does not work, the MCU and/or other semiconductors may need to be replaced.

Bill
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oootini



Joined: Oct 15, 2007
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PostPosted: Sun Jul 13, 2008 2:54 pm    Post subject: Reply with quote  Mark this post and the followings unread

ha. no it was just a crappy lead. it works perfectly. this little thing is seriously cool!
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State Machine
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PostPosted: Mon Jul 14, 2008 4:00 am    Post subject: Reply with quote  Mark this post and the followings unread

Quote:
ha. no it was just a crappy lead. it works perfectly. this little thing is seriously cool

Ah, bitten by the crappy lead syndrome Wink Good to hear man Cool

Bill
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oootini



Joined: Oct 15, 2007
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Location: ireland

PostPosted: Mon Jul 14, 2008 5:15 am    Post subject: Reply with quote  Mark this post and the followings unread

it's well loud. i presume this is because i have a 9 volt battery across it...i thuoght a circuit will take only the volrtage it needs from a power source. or is that current...
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catweazle



Joined: Feb 25, 2008
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PostPosted: Mon Jul 14, 2008 8:00 am    Post subject: Reply with quote  Mark this post and the followings unread

glad you got it running ootini Very Happy

About the LDO, thanks for correcting me, I was completly wrong... Embarassed
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oootini



Joined: Oct 15, 2007
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PostPosted: Mon Jul 21, 2008 1:14 pm    Post subject: Reply with quote  Mark this post and the followings unread

argh. more trouble. i built this when i had a week off at home at my parents house. i have a shitty little bass amp and this is what i played it through. even turned up to the max on the amp. the device was quiet.

now that i'm back home i plugged it into my mixer, and even when the gain and all the volume is full up the level is very quiet. i removed the resistor that was in front of the audio jack (as hanley previously mentioned) and substituted a numbert of values including just wire in place of the original res. no joy. the signal is still very quiet. i've tried changing the batteries to no avail. the voltage across the circuit is fine.

the voltage across pwm is of the magnitude -.1 to .4 volts. the 100nf capacitors i used were of +/- 20% tolerance. is it possible these are affecting the signal? the circuit works perfectly(i was playing with it for a week in my parents house), just a loooow signal...

any ideas??
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catweazle



Joined: Feb 25, 2008
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PostPosted: Tue Jul 22, 2008 11:07 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi oootini,
did you tried to connect the amp/mixer directly to pin17 of the PIC
(pwm output, 0..5 Volt)? maybe your capacitor to ground is wrong or
dead/shortet (should be 10nF = 0,01uF).
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oootini



Joined: Oct 15, 2007
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PostPosted: Tue Jul 22, 2008 1:04 pm    Post subject: Reply with quote  Mark this post and the followings unread

hmm. thanks. guess i'll try that. cheers.
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oootini



Joined: Oct 15, 2007
Posts: 80
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PostPosted: Tue Jul 22, 2008 3:09 pm    Post subject: Reply with quote  Mark this post and the followings unread

nope. replaced the 10nf cap and same thing.

then connected pin 17 straight to the mixer, and even though the signal was a little better i still needed the gain and volume all the way up to hear it...
Sad
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catweazle



Joined: Feb 25, 2008
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Location: germany
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PostPosted: Wed Jul 23, 2008 8:41 am    Post subject: Reply with quote  Mark this post and the followings unread

if you had connected the amp directly to pin17 (with no external parts)
the output should be very very loud. are you shure you have the right pin?
(only to be shure). maybe some soldering "dirt" between two pads,
did stressed the pic (short circuit, overvoltage >7volts) ?
Be shure all pots on the analog inputs produce a voltage 0 to 5Volt.
(maybe some unlucky parameters, it's possible that some parametervalues give no output, try different algorithms (pot 1).
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oootini



Joined: Oct 15, 2007
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PostPosted: Wed Jul 23, 2008 10:19 am    Post subject: Reply with quote  Mark this post and the followings unread

cool. i'll try all that. thanks again!

i definitely tried the correct pin.

Quote:
(short circuit, overvoltage >7volts) ?


i have a 9 volt unprotected battery across the circuit- is it possible i fucked up the chip? i thought you said earlier that the chip can take anythnig up to 35 volts...
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Blue Hell
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PostPosted: Wed Jul 23, 2008 10:34 am    Post subject: Reply with quote  Mark this post and the followings unread

oootini wrote:
that the chip can take anythnig up to 35 volts...


catweazle wrote:
the circuit itself (PIC) needs 5V, using a 7805 voltage regulator you can power it with up to 35V.


The PIC itself has every right to blow up on 9V, its specified up to 7V.

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catweazle



Joined: Feb 25, 2008
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PostPosted: Wed Jul 23, 2008 10:37 am    Post subject: Reply with quote  Mark this post and the followings unread

Oh oh sorry if that wasen't clear, I said ....
Quote:
The PIC itself can be powered directly between 4..7.5 Volts.

5 Volt is recommended, the 7Volt is the absolute maximum !!!
the voltage regulator 7805 can be powered up to 35V (with heat sink!!)
it regulates the input voltage down to 5Volt.

for a short time the pic should hold the 9Volts, I cannot say it is dead,
but it's shure possible. Tip: ever test your parts (ICs) if any get warm/hot if you build something and test for the first time.
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oootini



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PostPosted: Wed Jul 23, 2008 10:45 am    Post subject: Reply with quote  Mark this post and the followings unread

argh. thanks guys. i have the chip in a socket so its no hassle - i'll get a new one and should be ok then. thanks again for all your help. appreciated!
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yerpa58



Joined: Mar 08, 2008
Posts: 56
Location: Wisconsin
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PostPosted: Fri Aug 01, 2008 8:27 am    Post subject: catweazle, what version of CCS compiler did you use? Reply with quote  Mark this post and the followings unread

Hey catweazle,

That is a great little synth! I really enjoyed listening to the mp3 samples and reading your code. What version of CCS compiler did you use? It looks like you left some extra slots for more algorithms. I found the code to be very clear and readable, but I have never used #include with CCS compiler, I always stuffed everything into one big file. I like your method a lot better, and it is interesting that you use a variable sample rate for synthesis, gives it a real character of its own.

I am currently laying out a little board in Eagle, and will make the files available. Thanks again for sharing this cool design with us.
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oootini



Joined: Oct 15, 2007
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PostPosted: Thu Aug 07, 2008 2:42 pm    Post subject: Reply with quote  Mark this post and the followings unread

still haven't got round to getting another chip for this. but i will...
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oootini



Joined: Oct 15, 2007
Posts: 80
Location: ireland

PostPosted: Fri Sep 26, 2008 1:08 am    Post subject: Reply with quote  Mark this post and the followings unread

Got round to recording a little pic synth ditty, which you can find here: http://www.divshare.com/download/5454088-fea. finally got it working properly and have it housed in a natty little box. Unfortunately some of the synths don’t see mto make any sound when I select them. Weird. Maybe something is short circuited. Still, 3 out of 5 ain’t bad. looking for another PIC related project now. Can anyone recommend something?

Posted Image, might have been reduced in size. Click Image to view fullscreen.
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okvern



Joined: Feb 05, 2008
Posts: 78
Location: Seattle, Washington
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PostPosted: Fri Sep 26, 2008 7:48 am    Post subject: Reply with quote  Mark this post and the followings unread

Hi oootini,

re: "Unfortunately some of the synths don’t see mto make any sound when I select them."

The fractal synths have lots of settings that don't make any noise--usually, twisting the knobs will produce something. As far as I know, if some of the synths work, they'll all work, as they all use the same input/output paths.

Your version looks great!

Thanks,

Ole
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oootini



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PostPosted: Fri Sep 26, 2008 8:07 am    Post subject: Reply with quote  Mark this post and the followings unread

yeah it's wierd. the step sequencer one which i remember from my v1 chip was deadly, but that doesn't work and another synth functions weirdly and not as well as i remember. no amount of knob twiddling gets sound from them...
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yerpa58



Joined: Mar 08, 2008
Posts: 56
Location: Wisconsin
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PostPosted: Sun Sep 28, 2008 8:46 pm    Post subject: Reply with quote  Mark this post and the followings unread

Nice recording, ooootini,

What was used in making it? I have layed out a pc board for the fraktal synth but have not ordered it yet. I put the files on:

http://www.reprolabs.com/fraktal_synth_1.htm
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