Slide Pot question:

[dengel]

Any idea if these faders would do the job for the volume faders on a m64 unit?

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7585600419&rd=1&sspagename=STRK%3AMEWA%3AIT&rd=1#ebayphotohosting

http://www.nobleusa.com/slide.html

They are dual function, but I could just hook up one set of the contacts, right? Anyone have any experience with Noble's stuff?

Also - Plastic vs. Metal slider posts: which would you choose for MIDIBox application?

[moebius]

Any idea if these faders would do the job for the volume faders on a m64 unit?

Should work Ok!

They are dual function, but I could just hook up one set of the contacts, right?

Yup.

Also - Plastic vs. Metal slider posts: which would you choose for MIDIBox application?

This really isn't a factor for MIDIbox usage. It's more important that the "FEEL" is right for your application and faders are 'good enough' quality.

Moebius

[dengel]

Thanks, Moebius! It's my understanding that the pots have to be 10k - is that accurate? I found a great 1k micro rotary pot that is PERFECT for my install, which as pressed for space as I am would be great if I could use it.

Power dissipation at 12 volts is .012 watts. I am very very new to electrical circuits, so I guess what I am wondering is if these 1K linear roto-pots could be used for knobwork (like to control EQ settings, params, whatever) in a midibox 64? I don't want to burn things out.

EDIT: a search for 1K pots on the forums gives me the answer:

Thorsten Says:

I cannot recomment 100k pots because of the high impedance, the current drain will be so low that external noise can influence the measuring results too much. The result: jittering pot values. So, best values are around 1k and 10k.

They will work then, but now I have to figure out if power consumption would be OK. I want to have the following:

10 x 10k linear slide pots

38 x 1k rotary pots

Any idea of what formulas I need to use to determine if the voltage of the midibox64 can control that many knobs?

(BTW, in midi HUI section you can see the controller I am building).

[moebius]

Hi!

They will work then, but now I have to figure out if power consumption would be OK. I want to have the following:

10 x 10k linear slide pots

38 x 1k rotary pots

Any idea of what formulas I need to use to determine if the voltage of the midibox64 can control that many knobs?

It's not the voltage, but current consumption of the pots.. and if the PSU/regulator combination can supply that.

OHMs law! U/R=I

for 1k pots:

5v/1000ohm=0,005A

38x0,005A=0,19A=190mA

It's a bit on the high side and if you're going to use backlight LCD, the on board (Core) regulator might have heat issues.

Using a heatsink on the regulator is probably MUST. Also pay attention to PSU, it has to be able to supply enough current to power the thing up.

Moebius

[dengel]

Thank you, Moebius!

It's not the voltage, but current consumption of the pots.. and if the PSU/regulator combination can supply that.

Yeah, That's sort of what I meant. I won't be installing an LCD (the controller is customized for one program (ableton) and the LCD just isn't necessary.

What I should have said:

Any idea of what formulas I need to use to determine if the voltage needed to run that control arrangement is compatible with the Midibox core unit, and is there any special modification one might use when using 1K pots vs 10K?

Ohm's law (which I've been learning a bit about) seems to fit the bill. So, the core voltage of the m64 core is 5 volts, meaning each 1k pot draws 5//1000th of an amp, which is then multiplied by the number of pots to yield the total power draw of ALL the pots combined.

If 190mA is high, what TOTAL mA draw should I be shooting for to be safe for the core? For instance, the 10K pots will be

(5v/10kohm=0.0005)*10 pots= .005 amps per pot = 5mA total drain for all ten linear pots, right?

so, the entire amperage of my system is 195 mA, correct? How might I use this information to determine the requirements of my power supply wall-wart? I suppose I need a PSU that is capable of 5volts/200mA? If so, is any PSU that can provide that power of greater acceptable, or can I overdo the mA's and burn stuff out? Below the 195 ma stuff just won't turn on, right?

I apologize if these are rather elementary questions - I just can't afford to get things wrong and A) buy useless equipment B) burn something up  :o.

Have you guys seen a thread that goes over ways to protect the core? (I assume that is what the regulator tower thing does)?

Man, feeling stupid when learning totally new things is fun!

Don.

[moebius]

Ohm's law (which I've been learning a bit about) seems to fit the bill. So, the core voltage of the m64 core is 5 volts, meaning each 1k pot draws 5//1000th of an amp, which is then multiplied by the number of pots to yield the total power draw of ALL the pots combined.

Not bad not bad ;)

If 190mA is high, what TOTAL mA draw should I be shooting for to be safe for the core? For instance, the 10K pots will be

(5v/10kohm=0.0005)*10 pots= .005 amps per pot = 5mA total drain for all ten linear pots, right?

Yup!

so, the entire amperage of my system is 195 mA, correct? How might I use this information to determine the requirements of my power supply wall-wart? I suppose I need a PSU that is capable of 5volts/200mA? If so, is any PSU that can provide that power of greater acceptable, or can I overdo the mA's and burn stuff out? Below the 195 ma stuff just won't turn on, right?

No - 195mA is what the pots will draw. The modules will draw power too. You probably DON'T want 5VDC PSU ((wall-wart) as these are usually non-regulated) but something like 9VDC around 1Amp (800mA will work as well) and let the core regulator take care of voltage being regulated down to 5VDC. (the regulator needs some headroom to work correctly, around 1,5-2V and if you leave rectifying diodes on, there's voltage drop too - that's why 9VDC estimate)

The system will only draw as much current it needs and the PSU has to be rated above this. If you don't make bad mistakes (shorts) 'oversized' PSU is not going

to give you any troubles.

I apologize if these are rather elementary questions - I just can't afford to get things wrong and A) buy useless equipment B) burn something up  :o.

No wiring mistakes then! ;D

Have you guys seen a thread that goes over ways to protect the core? (I assume that is what the regulator tower thing does)?

Uhhuh, no?! Where?

Man, feeling stupid when learning totally new things is fun!

Uh, You're starting to 'GET IT' - the spirit!

Moebius

[dengel]

Moebius, your explanations are wonderful. Much thanks to you. :D

Any idea of what the power draw is of the core module for the m64? I have access to (at my local EPO) regulated PSU's rather than the standard noisy wall-warts. Would any extra safety be gained by using both the regulator on the board and the regulated 5v/1amp PSU? This is for Live use, so I am interested in making things as robust as I can, within economic reason.

[moebius]

Any idea of what the power draw is of the core module for the m64?

No idea - I *think* I've seen estimate around 200mA or something.

I have access to (at my local EPO) regulated PSU's rather than the standard noisy wall-warts. Would any extra safety be gained by using both the regulator on the board and the regulated 5v/1amp PSU? This is for Live use, so I am interested in making things as robust as I can, within economic reason.

Using both 5VDC supply and regulator at the core wouldn't work. But if you can get a good regulated 5vdc/1Amp supply You can wire it directly to core J2 and bypass the regulator (some minor mods needed). It would make sense as You seem to be building this to the case that easily can accommodate the PSU.

Moebius