Following on previous post on MIDI communication problems, I am going to talk now about external conditions that may affect hardware and thus make a device behave erratically or not at all.

Apart from having an easy fix problem like a broken cable, there are other issues that may arise from the use of MIDI systems on the road, specially in demanding conditions of atmospheric and physical maltreatment.

 

Hardware conditions

Electronics can be well designed up to a point of, what I call, “non return”. There is so much a Hardware designer can do to mitigate all the abuses the equipment will have in the field. Precautions can me taken, standards can be followed. None of them will ever be enough.

If issues of this nature arise, then it is the job of the designer to address it on the next revision, and record as much information from the users as possible. It is imperative that the designer knows in what conditions the equipment was being used.

Shock and trepidation can cause components to break, crack and bend from the soldering joints or event from their own bodies. If this happens then a serious of events will go through like a snow ball. Sometimes it is unpredictable but in others it can be mitigated in the design stage by using Failure Analysis to mitigate the Root Cause and minimize problems.

 

Temperature

At the design stage thermal issues are considered up to certain point, the so called “normal” usage of the equipment. If any component is broken, thermal protection design may not already be in place and the system goes on hurting it self even further.

Operating the equipment in all kinds of weather conditions is a priority for the designer. It is expected that it will work at 0°C and at least 85°C.

 

Here are some situations that can arise from this issues:
  • Broken cable that is carrying MIDI data and power supply, if the cable has been pierced or MIDI conductors are shorting with power conductors, then the MIDI hardware input interface will most certainly burn due to excess heat due to excess current flowing. Over current protection must be in place. Solution: use resistors where possible, PTC’s, fuses or polyfuses. Some components or areas on the circuit board may need extra thermal dissipation.
  • Overall Temperature will lead to extra current being drawn in the circuits and that may cause an over-current triggering the shut-down or further thermal runaway and magic smoke. Solution: addressed as above.
  • Meteorology adversities may also impact our equipments since they are connected to mains power. Power surges happens for different reasons but two of them most important are the extreme load that local mains circuit may have at the moment that, when the load disappears, mains voltage has a brief surge that can cause real problems to poorly protected/design equipments. Mains power will also transport thunder strike events that will decimate equipments connected in the area of the power station. This events are very serious and only hard-rock solid electronics designs will survive. Most of the equipments on the market are prepared to deal with events like these and they offer protections like mechanical circuit breakers or fuses. Solution: depending on the kind of circuit to protect, one may need to use MOV’s, TVS’s, Common Mode filters to filter mains noise and very subtle power interferences, fuses and circuit breakers.

 

We can put all this rhetoric in a nutshell, by saying that any MIDI system operating in the day-to-day of live/road events is in danger of this events to happen and should:

  • resume/continue operating with minimal or no external intervention
  • never endanger the user
  • never destruct the equipment it is connected to

 

Thank you very much for reading this last instalment of MIDI Problems and how to solve them. In a forthcoming post, I will give practical hardware examples of what to use to achieve this.