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Trying to build the Moon Base Xplorer AD/AR
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najls



Joined: Nov 04, 2020
Posts: 6
Location: Umeå

PostPosted: Wed Nov 04, 2020 9:40 am    Post subject: Trying to build the Moon Base Xplorer AD/AR Reply with quote  Mark this post and the followings unread

Hi!

New to the forum, and modular. And synths in general. And anything related to electronics. Bear with me.

I'm trying to implement the Moon Base Xplorer AD/AR envelope generator by PHOBoS. I'm building according to this revision (minus the LED stuff).

So far I've built it on breadboard, and it seems to be working, but there are a couple of things that worry me, and it would be great if someone could help me clear them out!

First, when I use a multimeter to read the output - in AR mode - I read a spike of around 17 volts when applying the gate signal. Is that bad? Should it be able to go that high? I'm only applying 12 volts to the circuit. The spike is only there for a fraction of a second and then it drops to 10 volts as expected. I've tried the output with my VCA (FSS VAC1 P.O.C.A) and it seems to be fine. In AD mode I read no higher levels than 10 volts.

Second, when switching from AR mode to AD mode the output is triggered once. When switching back to AR mode, nothing happens, but everytime I go to AD mode it triggers the output. I managed to remedy this by switching the 10K resistor going between the the 1nF cap and the transistor base to a 39K resistor, but I don't understand why that worked and if its bad in any way.

I should probably mention that I'm using a NE555P timer instead of the CMOS one. I've ordered the CMOS timer and plan to use that instead.

Ok, hope that made sense. Maybe I'm worrying too much, but hey, this is new and scary Smile
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PHOBoS



Joined: Jan 14, 2010
Posts: 5082
Location: Moon Base
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PostPosted: Wed Nov 04, 2020 5:56 pm    Post subject: Re: Trying to build the Moon Base Xplorer AD/AR Reply with quote  Mark this post and the followings unread

welcome party!
Quote:
First, when I use a multimeter to read the output - in AR mode - I read a spike of around 17 volts when applying the gate signal. Is that bad? Should it be able to go that high? I'm only applying 12 volts to the circuit. The spike is only there for a fraction of a second and then it drops to 10 volts as expected. I've tried the output with my VCA (FSS VAC1 P.O.C.A) and it seems to be fine. In AD mode I read no higher levels than 10 volts.

That's really odd. It would be possible to create a higher voltage but I don't see how that could be happening here, especially not with the zenerdiode and the opamps
which should both limit the output voltage. Do you also measure that voltage spike before the opamps, so across the zener ?

Quote:
Second, when switching from AR mode to AD mode the output is triggered once. When switching back to AR mode, nothing happens, but everytime I go to AD mode it triggers the output. I managed to remedy this by switching the 10K resistor going between the the 1nF cap and the transistor base to a 39K resistor, but I don't understand why that worked and if its bad in any way.

I just tested this and though it doesn't happen all the time for me it does indeed trigger sometimes. Hadn't noticed this before Rolling Eyes
I have an idea what might be happening and if correct it could be solved with an extra diode. Maybe a bit hard to explain where to put it
so I'll see if I can locate the schematic and make an updated version. Thanks for informing me about that.

Quote:
I should probably mention that I'm using a NE555P timer instead of the CMOS one. I've ordered the CMOS timer and plan to use that instead.

In this circuit it does indeed make a difference because of the resistor connected to the CV input which sets the treshold level in combination with the
internal resistors of the 555. For the CMOS version these have a much higher value. The CMOS version is also less noisy on the power when switching.

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najls



Joined: Nov 04, 2020
Posts: 6
Location: Umeå

PostPosted: Thu Nov 05, 2020 1:07 pm    Post subject: Re: Trying to build the Moon Base Xplorer AD/AR Reply with quote  Mark this post and the followings unread

Quote:
That's really odd. It would be possible to create a higher voltage but I don't see how that could be happening here, especially not with the zenerdiode and the opamps
which should both limit the output voltage. Do you also measure that voltage spike before the opamps, so across the zener ?

Well, it can't be ruled out that I made a mistake somewhere. I tried measuring accross the zener diode as well, and same thing there. 18 volts this time, but it drops immediately (I'm guessing the slightly higher spike might be due to changing out the 555 timer for the CMOS one, which I got today).

Quote:
I have an idea what might be happening and if correct it could be solved with an extra diode. Maybe a bit hard to explain where to put it
so I'll see if I can locate the schematic and make an updated version. Thanks for informing me about that.

I tried this again after changing to the CMOS timer and also replacing the 39K resistor with the original 10K again, and it triggers much less often now. Maybe once every 20 times. Maybe even less, so not that big of an issue anymore, although it would be cool to see your idea if you get the time to look into it Smile

Also, thanks so much for the warm welcome and informative answer! And of course for the curcuit - I'm having a lot of fun trying to build it, even though I don't understand everything (yet Razz )
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PHOBoS



Joined: Jan 14, 2010
Posts: 5082
Location: Moon Base
Audio files: 673

PostPosted: Thu Nov 05, 2020 2:59 pm    Post subject: Re: Trying to build the Moon Base Xplorer AD/AR Reply with quote  Mark this post and the followings unread

najls wrote:
Well, it can't be ruled out that I made a mistake somewhere. I tried measuring accross the zener diode as well, and same thing there. 18 volts this time, but it drops immediately (I'm guessing the slightly higher spike might be due to changing out the 555 timer for the CMOS one, which I got today).

Even if you made a mistake it's still odd to get a higher voltage than the supply. That makes me wonder if the diodes and capacitor on the output somehow
form a voltage doubler. It's interesting that it makes a difference with the CMOS version. Does it make a difference when you change the attack/decay times?
Also what do you use to measure it with as it might just be some sort of measuring error. Actually even if the voltage is higher it's weird that it passes though
the opamps aswell.

Quote:
I tried this again after changing to the CMOS timer and also replacing the 39K resistor with the original 10K again, and it triggers much less often now. Maybe once every 20 times. Maybe even less, so not that big of an issue anymore, although it would be cool to see your idea if you get the time to look into it Smile

yeah that's more in line with the results I got, it seems to vary a bit. I did find the schematic but what I had in mind would actually be a fix if it triggered when
switching from AD to AR mode. Something you could try is moving the 100K resistor that is connected to the base of the transistor to the other side of the 10K
resistor, so where it connects to the 1nF capacitor. Not sure if that would work and if it doesn't also try reducing its value. I'll see if I can do some tests this weekend.

_________________
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http://phobos.000space.com/
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najls



Joined: Nov 04, 2020
Posts: 6
Location: Umeå

PostPosted: Fri Nov 06, 2020 1:13 am    Post subject: Re: Trying to build the Moon Base Xplorer AD/AR Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
Even if you made a mistake it's still odd to get a higher voltage than the supply. That makes me wonder if the diodes and capacitor on the output somehow
form a voltage doubler. It's interesting that it makes a difference with the CMOS version. Does it make a difference when you change the attack/decay times?
Also what do you use to measure it with as it might just be some sort of measuring error. Actually even if the voltage is higher it's weird that it passes though
the opamps aswell.


Turns out the CMOS timer didn't make a difference with the spike. I measured again at the output and it reads around 17 volts, so the difference seems to have been between measuring at the output and across the zener. Should have checked that more thoroughly before!

I did however try with different attack/decay times and it seems the spike only occurs with the shortest attack time. Changing the decay time has no effect on the spike itself, but interestingly the spike only occurs when triggering the gate if the output is below around 3 volts.

Let me try and clarify. If I set the shortest attack time and the longest decay time (to get the slowest possible voltage drop and make it easier to read the output) I don't get a spike if I retrigger the gate before the decay has dropped the output signal to below around 3 volts. If I wait for the output signal to get lower than 3 volts or allow it to die out completely, and then trigger the gate, I get the spike. Did that make sense?

It feels like, when waiting, something is allowed to charge up, thus delivering the spike.

I'm using a basic digital multimeter (UT33A), which does make it a bit hard to read (the decimal place is all over the place Laughing ), but I'm certain I'm seeing what I'm seeing, though the meter might be wrong of course!


PHOBoS wrote:
Something you could try is moving the 100K resistor that is connected to the base of the transistor to the other side of the 10K
resistor, so where it connects to the 1nF capacitor. Not sure if that would work and if it doesn't also try reducing its value. I'll see if I can do some tests this weekend.


I'll make sure to try this as well and get back with the results!

EDIT: I have another super noob question. Can I use a separate jack for the inverted output instead of a switch between the two, and then use both the regular output and the inverted output at the same time? Embarassed Or will it blow up in my face?

P.S. I know it can't actually blow up in my face (my face will be under my desk with the rest of my body and I will reach up with a stick or some sort of hook to prod with, thus remotely triggering the gate, avoiding any large explosion).

EDIT 2: I finally got time to test this again, so I tried moving the 100K resistor like you suggested, but it didn't make any significant difference. The spike became a little lower at just under 17 volts. I don't know, maybe I should just let this go. I mean, it seems to be working fine! Maybe it is just my meter acting up or something.
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PHOBoS



Joined: Jan 14, 2010
Posts: 5082
Location: Moon Base
Audio files: 673

PostPosted: Sun Nov 22, 2020 2:01 pm    Post subject: Re: Trying to build the Moon Base Xplorer AD/AR Reply with quote  Mark this post and the followings unread

Quote:
EDIT: I have another super noob question. Can I use a separate jack for the inverted output instead of a switch between the two, and then use both the regular output and the inverted output at the same time? Embarassed Or will it blow up in my face?

yep, you can use both outputs at the same time if you like.

I wonder if this might be related to the voltage spike you're seeing. https://youtu.be/kRlSFm519Bo?t=1162

_________________
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najls



Joined: Nov 04, 2020
Posts: 6
Location: Umeå

PostPosted: Wed Nov 25, 2020 10:21 am    Post subject: Re: Trying to build the Moon Base Xplorer AD/AR Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
I wonder if this might be related to the voltage spike you're seeing. https://youtu.be/kRlSFm519Bo?t=1162


Ok, so I've been at this for a couple of evenings now, diving into documentation on the 555 timer and trying different caps and so on and nothing. Because I was an idiot and didn't test my crappy multimeter properly.

When nothing worked I finally pulled myself together and actually measured the gate signal coming into the module, and sure enough the spike was there too! So my next incorrect assumption was that something was wrong with my sequencer and that it was causing the spike. So i tried to apply 12 volts straight from a power supply to the gate input of the AD/AR and same thing there. In short - no matter what I measure with my multimeter I get the spike (I measured my laptop charger and it read 29 volts only to immediately drop to the correct 19). I guess I havn't used the multimeter that much and never reflected on it before. It was just easy to assume that the source of the problem was the mess of components and wires on a breadboard and not the tool I bought from an electronics company. So, yeah. I suck (but not as much as my multimeter (or are they supposed to work like this? (I'm definitively saving up for an oscilloscope))).

Sorry for putting you through all of that, and for ever doubting your circuit! Gonna try and solder it together as soon as I get some free time again. But nice catch with the Ben Eater 555 timer video! If I hadn't been an idiot, that would surely have been the solution Smile It was an interesting lesson nonetheless.

One final question though - do you have the specs for the last transistor and resistor connected to the LED? I very much feel I need the blinky light.
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PHOBoS



Joined: Jan 14, 2010
Posts: 5082
Location: Moon Base
Audio files: 673

PostPosted: Wed Nov 25, 2020 11:19 am    Post subject: Reply with quote  Mark this post and the followings unread

well, at l(e)ast you found the problem so that's a success if you ask me. I still want to look into the triggering thing
to see what exactly is happening there though it's not much of a problem in use.

I must have forgotten to label that transistor but it's most likely a BC547B, anything similar should work fine.
The resistor value depends on the LED you use and how bright you want it to be so that needs some experimentation.
I used a blue LED myself which are very bright and don't need much current so I probably used something in the range
of 47K...100K. For other LEDs I usually use something between 1K..10K. You can also play around with the resistors
connected to the base of that transistor to alter the response.

_________________
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http://phobos.000space.com/
SoundCloud BandCamp MixCloud Stickney Synthyards Captain Collider Twitch YouTube
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najls



Joined: Nov 04, 2020
Posts: 6
Location: Umeå

PostPosted: Tue Dec 01, 2020 3:32 pm    Post subject: Reply with quote  Mark this post and the followings unread

Ok, a month later and I'm done! Switched out the 500K pots for 200K log pots I had laying about, which I felt gave better control when setting short time spans, the trade-off being shorter maximum time spans. Other than that it's according to your original schematic. Works a charm!

Since I don't have a good way of making panels I used one of the placeholder panels that came with my case. Didn't bother to try and cut it. Instead I think I'll just try and fill the width of the panel with DIY modules, so expect more confusing threads like this one from me in the future Very Happy

PHOBoS wrote:
I still want to look into the triggering thing to see what exactly is happening there though it's not much of a problem in use.


I'll keep a lookout for any update on that on the forum, though I'd say that at least in my case it's a non-issue.

Anyway, THANK YOU SO MUCH for all your help (and patience)!


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PHOBoS



Joined: Jan 14, 2010
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PostPosted: Wed Dec 02, 2020 10:37 am    Post subject: Reply with quote  Mark this post and the followings unread

oh that looks great! both stripboard and panel Very Happy
I love the insulation on those tiny jumpers love
great idea using the red part on the power headers, why did I never think of that ?!

glad I could help, I hope you'll have a lot of fun with it.

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kaputtpanzer



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PostPosted: Wed Dec 02, 2020 3:05 pm    Post subject: Reply with quote  Mark this post and the followings unread

Well that's a super tidy perfboard build Cool excellent work
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najls



Joined: Nov 04, 2020
Posts: 6
Location: Umeå

PostPosted: Sat Dec 05, 2020 2:02 pm    Post subject: Reply with quote  Mark this post and the followings unread

PHOBoS wrote:
oh that looks great! both stripboard and panel Very Happy
I love the insulation on those tiny jumpers love
great idea using the red part on the power headers, why did I never think of that ?!

glad I could help, I hope you'll have a lot of fun with it.


Thanks so much! I like paying attention to details (and those tiny bits of insulation could mean the difference between life and death Laughing )

kaputtpanzer wrote:
Well that's a super tidy perfboard build Cool excellent work
Thank you! Only took four iterations in VeeCAD and about 6 hours to put together Rolling Eyes
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