Latch doesn't work with keyboard or sequencer?

Hi

I’m trying to use a latch with the Synth Kit.

This works … power—button–latch–oscillator … but this doesn’t … power–keyboard(hold)–button-latch-oscillator. It doesn’t work with the sequencer instead of the keyboard either.

Why is this? power–keyboard–button–oscillator works with the button as a momentary switch. Why not if the latch is placed afterwards?

Thanks
Mark

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Hello @tricol,

I think the issue is digital/analog. Just one question. are you using the micro-sequencer bit, the one with the four dimmer, or the sequencer bit, the one with the eight outputs?

A look into the schematics of the latch bit sometimes helps.

The latch is a pure digital circuit. It has a schmitt-trigger input buffer and the clocked D-flipflop. It will only work, if the input signal has a certain level and also clearly returns to “low” which is about 0V.

The bits from the synth kit are basically analog bits. They output and accept analog signals in the range from 0V to about 5V.
By default the power bit has a “high”, 5V output on the signal pin. Therefore it is no surprise that the first combination, [power] - [button] - [latch] - [oscillator], works.
The keyboard bit is designed to output analog values equivalent to certain notes. It might not reach appropriate levels to fullfill the requirements of the latch bit. However, I assume there should be some combinations that will work.
Hope this points you into the right direction.
best regards
7th Dwarf

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Thanks for the explanation! It’s the micro-sequencer I’m using. I did find this video where the latch seems to be working in between the micro-sequencer and a keyboard so that the keyboard channel runs at half time.

Not sure why this one is working. and none of my tests did.
I’ll do somemore experimenting.

Thanks
Mark

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Hello @tricol ( Mark ),

I think they turned the last pot of the micro-sequencer bit to a quite high level, and then it works.

Let’s go technical. The input of the latch bit goes to a schmitt-trigger buffer. The NC7WZ17 is a ultra-high-speed, TinyLogic version of a non-inverting buffer. The threshold voltage for a high signal is about 2.5V. Means, if you apply a voltage of more than 2.5V to the input of the latch bit, you will generate a positive edge signal for the D-flip-flop and it will toggle. Of course, I assume that the voltage level on the input is around 0V before, which should be the case for the micro-sequencer.

Please apologize that I’m talking like a blind about the colour, as I do not have any of these bits here in front of me. But from the theory it should work.

best regards
7th Dwarf

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Thanks very much. This is all really helpful.
So I need to up the pitch so it’s over 2.5V equivalent?

Mark

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The trigger out of the keyboard or sequencer should work to flip the latch (the bitsnap coming from the top of the keyboard and sequencer) I’m not sure what you are trying to do with the sound, but if you want to turn something on and off every other note you could use the trigger out to flip the latch as it is just a high low signal. For example if you wanted to modulate the filter every other note you could have a normal synth circuit then have the latch on the trigger out of the keyboard or sequencer/oscillator/filter freq in.

I just took a look at the video above regarding the clock divider and it looks like they are running the latch off of the trigger out of the sequencer. As that is a high low signal it will be enough to flip the latch. If you try and run it from the normal output bitsnap (the one in line not the top) it may not go high enough to flip the latch as SeventhDwarf explained.

Hope that helps!
Thank you.

Thanks!
I’ll try to set it all up with the trigger instead…