gatelength 0 - is that no gate or a very short trigger?

MIDIbox SEQ
1

Hello

While i´m still waiting for the parts and pcbs, i´m planning and planning all the applications i want to build…

As described in the manual, the gatelength of a step can be selected in steps from 0-100%.

When set to 0%, do i get nothing or a very short pulse?

My Plan is this:

Design a drumbox that can be controlled by a Midibox Seq and MBCV in many cool ways. Thant´s more of my thing, analog design. Of course i´m looking forward to sharing my results to those interested!

For some sounds it could be useful to controll the length.

So instead of triggering an Release envelope, it could be gated. A simple envelope would then react like a Sustain/release env.

Or, for stuff like reversed cymbal sounds, the MBSEQ/CV  could gate a ASR envelope.

Together with the cv-outs this could make a really dynamic analog drumbox.

It depends on how useful the difference between 0 and 23% gatelength is, for this special use.

I guess it could be changed quite easily in the code (?), but that might only be a good idea if drums in the way described are the only use for the SEQ. I suppose for “normal”, melodic lines and everything else, it´s best the way it is.

2

I like the idea to vary the gatelength for controlling an envelope, but I can also say, that the current implementation is not sufficient for that what you are planning.

The gatelength of a step is quantized into 24 microsteps, derived from the internal or external MIDI clock. In order to improve the readability, the MBSEQ doesn’t display the number of steps, but the relative gatelength in percent (4%, 8%, 13%, 17%…100% and Glide). There is no 0% as 0% means no gate (trigger switched off)

This quantisation is perfect for common patterns, as it scales with the BPM.

But I think that you are searching for a way to enable the gate for a specific time. E.g., from 1 to 127 mS in steps of one mS, independent from the BPM, and maybe controlled with the velocity (advantage: when an event layer is setuped for Drum mode, you can control 3 drumlines with variable velocity from a single track)

Best Regards, Thorsten.

3

Yes, thought it would be like that. The Seq is just not made for what i have in mind.

On the other hand, having the possibility to controll the gatelength relative to the speed is a very powerful feature!

Iremember one of my first diy projects. It was a sequencer based around two 4017 cmos counters. It has many cool features like parallel/serial mode, independat clock division, VC reset, VC glide on/off, VC pause, swing feel and variable gatelength. The last two are not relative to the clockspeed. I found no way to do this with cmos. It contains propably 20* the parts of a MBSEQ… and has 1/1000 the features. My myspace page shows the inside…

But there is still a solution for what i´m planing.

A second CV can be used to modulate the gatelength (outside the seq, in an little circuit). For a whole drumbox it´s not reasonable maybe, as you need twice the aout chanells, but maybe i will implement it for some of the sounds.

Another way to make the patterns more dynamic could be to controll the release of the envelope, or the gatelength with the velocity-cv from the AOUT module.

This is propably the best way to do this. I will first design a drummodule that does all that. Controll with one or two cvs of how soft/hard, silent/loud, long/short, bright/dark, high/low, noisy/clean the sound will be.

That´s propably more than you need, and too many pots to keep it “simple” to use.

More for experimenting, see what´s a feature i don´t want to miss, and what can be ommited.

Then another good way to save pots and space is to see what mod destinations are useful, have one pot for mod intensity and a rotary switch for some destinations.

A single pot can also be used to controll two destinations in one turn, or blend between two destinations. I don´t want another modular, but a nice and handy drumbox…

If something like this is well trimmed it can be very musically and easy to handle.

There will be a ducumentation on this somewhere, but that´ll take some time…

My aim is to do what i can do -  design analog soundmakers, and build them around your projects as good as i can. Many cool possibilitys lie in those midiboxes  ;D and rather than midify an existing analog circuit, i´ll try to have that link from the start.

4

Where can I adjust percentage of gate length?

I would like to drive solenoids with this pulse but I think 1us might not be enough.

5

Where can I adjust percentage of gate length?

I would like to drive solenoids with this pulse but I think 1us might not be enough.

With solenoids you need to be thinking in millisecond terms - microseconds is way too short for most of them.

6

I know, that`s why I want to increase the gate length. You know where is the setting for it?

7

It’s normaly in Layer C

Best Regards, Thorsten.

8

Oh, is that so. I thought gate length needs to be changed and recompiled. That is good.

Just another question please.

How long 100% last, roughly? Or is 100% is Glide how much 99% last. Should it be enough to drive solenoids?

I think 0.5 sec pulse should be enough.

9

Moment, you mean the length of the 1 ms triggers, right?

This length cannot be modified, because it directly depends on the SRIO chain sample rate.

As described in my first answer of this topic, the current implementation doesn’t allow to vary the length. And a solution is really not so easy, otherwise I would spend an hour and hack it into the firmware for you…

Best Regards, Thorsten.

10

Why do you want to use triggers instead of the normal gatelength (which depends on the BPM rate, and which is fineadjustable in 24 steps for each 16th note)

Best Regards, Thorsten.

11

I might understand this wrong, bu my idea is to use gate out pulse to drive solenoids over ULN2803.

I did that before with MB64 for experiment but there I can define note length in software so I could power the solenoid long enough to get good punch.  :slight_smile: 1ms pulse is not enough.

I thought it would be really cool if I could trigger mechanical percussions Im working on directly from SEQ gates. Is there some elegant solution for this? I dont want you to bother writing custom code just for me. If gates cannot be used to triger solenoids, Ill concentrate on the other workaround.

And, thank you for your answers Thorsten.

12

I think that the common gatelength function is exactly what you need.

E.g., at 120 BPM a single 16th note can control the length from 5 mS to 125 mS in steps of 5 mS

By using the global clock divider in the BPM menu, or a local clock divider in the track div menu, you can scale the length by a certain factor. If you are using 4 (as an example), the resulting gate length would be 20 mS .. 500 mS in steps of 20 mS.

So, this approach is sufficient for gate lengths > 1 mS, only disadvantage: the length depends on the BPM rate. But I guess that it won’t be a big problem for you to re-adjust the gatelength in layer C whenever the BPM rate is changed dramatically.

Best Regards, Thorsten.

13

I’m thinking that whatever you do, it might well be worth opto isolating the gate outputs from the hammer drivers. Solenoids kick out a lot of spike, which could kill the micro. As an aside, with 3 fast opto’s it would be possible to isolate a DOUT or AOUT, which I’ve been thinking about recently. Because of the high voltages in an analogue synth, (+/- 15 Volt supplies and 10V control signals) and the possibilityl of damaging the sequencer by bad patching.

14

Thanks TK, I understand everything now, and will continue as I imagined.  :wink:

Mike, I dont think I need a optocouplers when Im going to use ULNs as a bridge to solenoids, do I? :-\ If I need to, please tell me some suitable fast optocouplers that can be driven by SEQ gates.

15

Perhaps it’s just me worrying too much: I do a lot of work with industrial control systems, and whenever we’ve had problems it’s been something in the outside world of the machine upsetting the micro.

I’ve got some very scary horror stories too: like the toolpost box on a CNC lathe that had a low voltage position sensing switch wired direct to an I/O card on a PDP11 computer, (old, well cool mini computer), and a mains operated positioner, nicely opto isolated from the control gear. Very good, until someone got a coolant leak. Then the liquid joined the sensor to the mains drive and put 240 Volts onto the DEC Q-Bus. Tough old birds those PDP11’s, I only had to rebuild the IO card.

More recently, a local company added a colour pellet doser to an injection moulder. we kept having what seemed like random control hangups, until I found that in installing it, they’d connected the doser direct to a spare IO, (as per the handbook), this let motor noise from the doser on to the controller ground, and was causing random triggering of other IO. A very basic opto cleared that.

I may have got this wrong, but you seem to be thinking of driving the xylophone direct from a sequencer. The more I think about it, I would prefer to make another basic core, and do a MIDI to solenoid unit, like some of the organ guys, then a whole lot of things could be MIDI driven, (like my Christmas lights…)

On the solenoid idea, I think I’ll try it out. Here are my thoughts to get it going.

  1. use a relatively high voltage for the solenoids, then you won’t ‘starve’ the power supply if you ‘fire’ more than one at once. I was thinking of 24V. This also reduces the current, and there is less risk of damaging the ULN. ULN’s will deliver 500mA from one output, but this drops proportionally as more are used at once, ending at 120mA if all are being used. This might not be enough for some solenoids.

  2. get some decent, FAST spike killer diodes. Some ULN have then built in, but they may not handle the reverse kick from the large solenoid coil.

  3. The 24V supply does not have to be regulated, just  a reasonable amount of capacitance to feed the solenoids.

  4. if the xylophone hasn’t got too many bars, perhaps a 555 pulse stretcher might be the way to go for now, I can get 555’s for £0.15, so each pulse stretcher might cost less than £0.50. There is the option of tuning the pulse lengths with a trimpot, which might help get a more even tone. This is messy, but the 555 will drive a cheap Darlington transistor or power MOSFET, and you wouldn’t need the ULN’s.

If you went for a MIDI to Solenoid unit, then the pulse widths could be re-written in software. I really do need to take the usual advice and dig into the Wiki, because I think this has already been done.

sorry for rambling

16

Mike, thanks for the long post. I have alot of good ideas but my problem is I`m not that good with electronics nor programming, so i can just integrate some design into my idea, and not design one from scratch.

  1. if the xylophone hasn’t got too many bars, perhaps a 555 pulse stretcher might be the way to go for now, I can get 555’s for £0.15, so each pulse stretcher might cost less than £0.50. There is the option of tuning the pulse lengths with a trimpot, which might help get a more even tone. This is messy, but the 555 will drive a cheap Darlington transistor or power MOSFET, and you wouldn’t need the ULN’s.

That sounds like something I was thinking of… It must be some way to made short pulse last as I desire by adjusting some kind of hold trimmer. So, pulse stretcher, you say. Do you have some schematic I could use?

I must say, I will use rather different kind of solenoid - a HDD head actuator. It is powerful enough, probably because of neodium magnets and dont have much of winding so maybe they induce less current that can potentially damage the driver. I already made small rig with beater and pulse it with just few volts, and It strikes pretty well. :slight_smile: Is there something you advise me to check about them? I think they are perfect for all I want to do, and its recycled. Ive been wondering around for a long time for something I could use instead of winding my own solenoids, and I feel this could be the way to go. What do you say?

17

I think the HDD actuator idea is brilliant, though they do eat quite a bit of current. Later on, it might be possible to make a variable impact driver with these - so it might decode the MIDI volume, (though not that well)… Anything to avoid coil winding!

I think an old HDD is going to be dismantled next week. I’ve been recycling them, selling the alloy for scrap, and using the magnets for stage prop work. Put up a thin steel strip, and they are great for hanging drapes and background cloth.

My first go used old relays, with a hammer stick glued to the actuator, they are quite noisy though, better when I put some felt on the top of the coil.

I’ll get busy with a 555 based design.

I’ve been looking for a child’s toy xylophone this week

18

i saw an interesting site about diy player pianos the other day.

had info on solenoids and using velocity to control strike.

i can find it again if you are interested…

19

Here are few pix of testing.

Beater is actually mothers needle for making sweaters, what you call it on English? It is too heavy and will be replaced with aluminum and paper ball instead of plstic. The paper ball is pretty hard but lightweight so beater will be possible to move more aggressively. I think HDDs head actuators are perfect too because they dont need the spring for 0 position. :) I just love my new percussionist and need to find him company. Another thing that is not imortant is that I didnt took out the electronic so I rewire the PCB and have working SMD LED in parallel to the HDD head so it lits up by the pulse.  :slight_smile:

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:o A knitting-needle hard-disc robot-drummer.

It’s an abomination against Nature. I love it.  ;D