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Anushri input protection
MUFF WIGGLER Forum Index -> Music Tech DIY  
Author Anushri input protection

okelk

I've been studying the schematic of the Mutable-Instruments Anushri (partly because I'm interested in ssm2164 designs and partly because I may build one for a friend....)

http://mutable-instruments.net/static/schematics/Anushri-revC.pdf
http://mutable-instruments.net/static/schematics/Anushri-Control-revC. pdf

What I don't understand (or maybe just don't find in the schematics...) is:
The anushri runs internally from +/-5v, but It's supposed to be eurorack compatible and don't see any protections from voltages over/under +/-5v (clamping diodes or such...)...

How does this work? Or does it?
I want to be absolutely sure that I don't have to add any input protection before I order a pcb...


cereyanlimusiki

Instructions for converting Anushri from DC power to Eurorack suggest you need to remove LT1054 chip but I do not whether this is what you are looking for.

Why don't you ask in MI forums. Olivier is always helpful and answers questions promptly


okelk

cereyanlimusiki wrote:
Instructions for converting Anushri from DC power to Eurorack suggest you need to remove LT1054 chip but I do not whether this is what you are looking for.

Why don't you ask in MI forums. Olivier is always helpful and answers questions promptly


thanks, but that's not what I'm searching for...the lt1054 is just a voltage inverter that provides the negative voltage for the -5v regulator...

...If nobody can help me here, I guess I'm gonna ask at the mutable instruments forum...


pre55ure

So it's not necessarily helpful, but I couldn't find any voltage protection either. Looks like the inputs go straight to the 4051 and then to the ADC input with no protection.
Maybe it's expected that you will mod it if your planning on using it with other equipment? hmmm.....


onlyHzwhenI...

If you do get an answer to this elsewhere please report back here if it is not too much trouble. I'm sure there are a few of us here that would love to not destroy our Anushris. Or worry over actually thinking about what the other end of that cable is hooked to.Dead Banana

Thanks,
~JT


neil.johnson

Had a quick look at the schematics, and on the PSU page I don't see any reverse-voltage protection or missing rail protection (important for the 2164).
Oh, and be careful with the power header - pins 1 and 2 correspond to the stripe (-ve) on a properly fitted polarised header.

Neil


daverj

There doesn't appear to be any input voltage protection on the jack inputs. There is no current limiting on the outputs, though they should be OK for temporary shorts such as during patching.

The wall wart power input is reverse power protected, but the Euro power input is not.


pichenettes

Quote:
The anushri runs internally from +/-5v, but It's supposed to be eurorack compatible and don't see any protections from voltages over/under +/-5v (clamping diodes or such...)...


The Euro power connector is not protected around reverse polarity.

The gate and trigger inputs are overvoltage tolerant up to 16V (the kits were sold with 74HC4050s, which have built-in clamping diodes).

The CV inputs all consist of resistors going into the virtual ground of op-amps. Worst case scenario is that the op-amp will clip. I'm not sure why you'd need clamping diodes there, besides ESD protection.

The CV outputs tolerate temporary shorts.


daverj

pichenettes wrote:
Quote:
The anushri runs internally from +/-5v, but It's supposed to be eurorack compatible and don't see any protections from voltages over/under +/-5v (clamping diodes or such...)...


The Euro power connector is not protected around reverse polarity.

The gate and trigger inputs are overvoltage tolerant up to 16V (the kits were sold with 74HC4050s, which have built-in clamping diodes).

The CV inputs all consist of resistors going into the virtual ground of op-amps. Worst case scenario is that the op-amp will clip. I'm not sure why you'd need clamping diodes there, besides ESD protection.

The CV outputs tolerate temporary shorts.


J1 and J3 go directly to inputs of a 4050 powered by +5v and ground. If a 74HC4050 is used, while tolerant of positive signals to 16v, it can't handle inputs below -0.5v. If driven by a bipolar signal from an op amp, depending on the output configuration, it could exceed the -20ma clamp current and pop that chip. A 1K series resistor on each input would solve that. Optionally with Schottky shunt diodes to ground.

A pair of series diodes on the Euro power input would solve reverse power protection, since the diode drop wouldn't effect the voltage needed by the regulators.

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