VC Master Clock with PWM - PCB run

diablojoy · Posted: Thu Mar 17, 2011 3:03 pm Post subject:

will have to wait for the weekend not sure if i have any 4016 on hand but hopefully i can try some things out then
I will get back to you

fonik · Posted: Mon Mar 28, 2011 12:57 am Post subject:

hey diablojoy. i moved your posts to a new thread, showing your efforts in developing an advanced sync for this project. i assigned this new thread to you. hope you're fine wth that!?

Advanced Sync for the VC Master Clock

diablojoy · Posted: Mon Mar 28, 2011 1:14 pm Post subject:

yes very fine with that and thank you Smile

diablojoy · Posted: Sun Apr 10, 2011 12:21 am Post subject:

A couple of pics of a quad build
not finished yet but working and calibrated
still to add my mods
the wiring is a bit messy and took three times longer than it should have Embarassed

but I am down to only using my left arm at the moment . I have carpel tunnel syndrome in my right which has been really bad for the past week can't grip anything , well thats my excuse and i'am sticking to it Laughing

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emdot_ambient · Joined: Nov 22, 2009 Posts: 669 Location: Frederick, MD

Very awesome build! The wiring might have been a pain, but it turned out very neat and organized. I like that.

marvkaye · Joined: Mar 14, 2011 Posts: 222 Location: Fla

I know most of the focus on this project has moved over to the sync thread, but I've got a question about the basic VC clock circuit. Since the boards are sold out I've done a stripboard layout for it (be happy to post it if anyone's interested, and if Matthias doesn't mind) and have it mostly populated. (It's actually a dual board, with two complete VC clock circuits...) I used the circuit notes to include the various options, even set it up for the tempcos to achieve 1v/octave tracking. Then it occurred to me, this is a clock, not an oscillator, so why would I need 1v/octave tracking? Is there an implementation imagined for this thing where you raise the clock rate all the way into the audio range and use it like an oscillator? If that's the case, shouldn't there be a frequency range selector of some sort to select whether you want to use it as the clock to drive a sequencer vs using it as an alternative oscillator? (I apologize if these are really stupid questions, or if it's been discussed already... I've just had a hard time wrapping my brain around why someone would need 4 or 8 or 12 of these if all they want to do is control the speed of their sequencer.... I'd really like to get a better understanding of its uses.)

Thanks in advance....

<Marv>

fonik · Posted: Sat Jul 16, 2011 1:47 pm Post subject:

marv,

1st: feel free to post your stripboard layout. we are on the DIY forum, and it is all about sharing, isn't it? anyways, thanks for asking...

2nd: i still have 5 of these little PCBs laying around, so they are not sold out yet (maybe i stored them for someone who wanted to pay later down the road and simply forgot about it? i dunno).

3rd: the core is actually based on the TB303 as seen in the old EFM bassace. so why not using it as a VCO?
IIRC someone asked for 1V/oct in the forum here, so i implemented it in the docs.

edit:
4th: the original idea of using more than one board was to have one master several slave boards. this way one could play with different settings and voltage control of the comparators - if needed.

marvkaye · Joined: Mar 14, 2011 Posts: 222 Location: Fla

Thanks, Matthias, I thought the stripboard layouts would be welcomed, but since you're selling the PCBs I felt it only right to ask first. That being said, the pictures are posted below.

Some comments....

The trimmers need to be the little teeny top-adjust types that are only 3/8" (or better yet, 1/4") square. The tradeoff is precision, I guess. You can get 3/8" square in 25 turn, but the 1/4" square are only 12 to 15 (at least based on what I've seen.) I'll probably opt for the 12 turn Muratas from Mouser... they're 1/2 the price of 25 turn Bourns trimmers. Sometimes economics needs to be in control. Wink

In order to fit the trimmer T1 you need to nudge R9 closer to R10, so leave a little extra on the R9 leads and maybe don't mount it perfectly tight to the board. That way you can fudge it over the little bit required. (At least this is what I ran into when I tried one of the 3/8" trimmers I had in my stock.... this is another reason I'm leaning to the smaller trimmers.)

Trimmers T2 and what I called T-J1 (for the one that connects between the regular circuit and J1 to accommodate the 1v/octave trimming, as outlined in the circuit notes) are both installed horizontally. This necessitates cutting the copper strip between their terminals (ie, between drillings) with a razor knife as opposed to the usual trick of simply drilling the copper away at the holes. I've detailed those cuts in two separate photos.

The wire jumper that carries V+ from the hole next to R7 down to pin #4 of the TL074 needs to be insulated instead of bus wire. This is because the collector lead of Q2 has to pass over it in order to connect to the standing vertical lead of R7... the insulation should prevent a short there.

The short vertical jumper just below R7 should be a little loop (ie, standing proud of the PCB surface a bit) in order to have an easy place to connect the left lead of the tempco.

I'd have preferred orienting Q1 and Q2 face to face to improve their thermal contact for the 1v/octave option, but I think if you squeeze them together til they touch and epoxy them and the tempco into a single lump, this orientation should probably work just fine. I guess we'll see.

Just so you know, I haven't finished populating my board yet, as I need to order the little trimmers, won't have them until next week sometime. This means that this layout is untested except for using the test function in Lochmaster. And if you'd like a copy of the Lochmaster .rst file, just drop me a PM or email me at marv at lancair dot net... I'd be happy to share it.

Enjoy!!!! Wink

____________
<Marv>

edit 10/8/12... the transistors below the LED pads at the upper RH side of each layout should have been labeled Q4, 2N3904. Sorry. Note added to picture file comments to that effect.

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Single VC clock stripboard layout, component side Please note: the transistor below the LED pad at the upper RH side of the board should have been labeled Q4, 2N3904. Sorry. As soon as I figure our how to upload a revised picture I'll make the correction

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Single VC Clock stripboard layout, copper side

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VC_ClockX2_SB_top.jpg

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Double VC Clock stripboard layout, component side. Please note: the transistors below the LED pads at the upper RH side of each layout should have been labeled Q4, 2N3904. Sorry. As soon as I figure our how to upload a revised picture I'll make the correc

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Detail of knife cut between drillings to accommodate the horizontal mounting of trimmer T2

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Detail of knife cut between drillings to accommodate the horizontal mounting of the trimmer that heads out to J1 as per the circuit notes

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prgdeltablues · Joined: Sep 25, 2006 Posts: 141 Location: UK Audio files: 8

Finished building a dual (Master/Slave) VC Clock - excellent compliment to the Klee, really adds to the musicality. I have a couple of questions.

I'm using 12V, and in the build documents it says to change R12 to 20k and R14 to 15k to adjust the PWM response. On the schematic, R12 is the 100k resistor between the clock and the positive input of the comparator. Should that have said R13 - the top end of the voltage divider around the PWM pot?

The circuit seems to work well enough, so I guess the value of R12 isn't critical.

At some combinations of PWM pot setting and PWM CV, the output holds - for example, when I put a 0-5V square wave into the PWM CV, when it is at 0V, the output clocks as expected, but when the CV goes high to 5V, the output stops clocking. That seems to make sense, as the PWM CV and PWM pot are averaged into the negative input of the comparator. So if they average to more than 5V, the positive input (from the clock) will never exceed the negative input, so the comparator stays low. Is this the intended behaviour? It's quite cool!

I had to add 100k pull-down resistors to ground at the point marked JP2 on the schematic, where I've installed an on/off switch for the Master clock, as otherwise in the off position the output went haywire (every pattern light on the Klee was lit for a few seconds, then it stopped, but if I moved my hand near the switch, it would clock erratically). Realised this was because with the clock disconnected from the comparator, the positive input of the comparator was left floating. Any one else had that problem?

Peter

fonik · Posted: Fri Oct 28, 2011 8:53 am Post subject:

inlifeindeath · Joined: Apr 02, 2010 Posts: 286 Location: Albuquerque, NM

fonik, i just corrected the resistor values and it works like it should. Thanks prgdeltablues!!!

Paradigm X · Joined: Feb 15, 2011 Posts: 252 Location: Null and void

Is there interest in another run/anyone have a spare knocking around?

Many thanks, Ben

EDIT : Many thanks to the person who provided me with one PCB Smile

Youve not made yourself known so I havent made your name public, but cheers Cool

ringroad · Joined: Feb 28, 2012 Posts: 5 Location: Coventry, UK

Just finished building this one from the stripboard layout kindly posted by Marv. It works happily, with one small alteration - the transistor next to the LED on the right should be labelled Q4 and is a 2N3904 rather than a 2N3906.

marvkaye · Joined: Mar 14, 2011 Posts: 222 Location: Fla