Blind electronics

From JookWiki

Doing electronics blind is a headache for a bunch of reasons. This page goes through the ones I've encountered second hand and any possible solutions I've come up with for them.

This page is targeted at those with total lack of vision, may or may not have hearing, and have their other senses and a good range of motion. If you're outside those areas I'd be interested to talk with you and brainstorm how to get past your challenges.

Touching components[edit | edit source]

Tactility is the name of the game when it comes to navigating the world blind. The same is true for electronics. However there are various risks:

Hot components[edit | edit source]

Electricity creates heat, sometimes at temperatures where touching will cause a risk of burn. I would say there's two categories of heat to deal with: Controlled and uncontrolled.

Controlled heat is what you would expect from a functioning design; Heat is an enemy to electronics too as it can damage components or change power consumption. A working design found in a manufactured product control heat using heat dissipation devices such as heat sinks. My recommendation on dealing with these components is to be careful as if you're touching something like a plate or a cup:

  • Touch it briefly to see how hot it is then decide whether to touch it again
  • Use the back of your hand to touch if needed
  • Power off and wait for components to cool if possible

Uncontrolled heat happens due to a fault or bad design. The danger from this heat is that it's unexpected and results in a burn or fire. Usually you can detect uncontrolled heat through the following methods:

  • Touching a component (can result in burns, not recommended)
  • Smell from melted plastic or melting components

I do want to make it clear that heat here comes from passing current through components. If you suspect something is going wrong, remove the current source (usually by just turning the device off) to avoid causing more heat.

Batteries can be especially problematic in this case if there's no way to stop the current and thus heat. If you're using batteries make sure there's safety measures in place to stop the current, such as a fuse.

Powered components[edit | edit source]

Touching a component can potentially add you to a circuit. Depending on what type of circuit this is this may do nothing, it may damage the component, or it may damage you. There are two particular categories of circuits you should watch out for: Low voltage and high voltage.

The human body does not conduct much electricity at low voltage (I'll use 12 volts as my conservative definition here) so it's unlikely you'll damage yourself by touching a component. It is possible to damage components by unintentional paths between components. There main technique to avoid this is to touch only the ground parts of the circuit such as metal USB or Ethernet shields.

High voltage is a different story (I'll define it as over 50 volts here) as your body may conduct enough electricity to shock you. Do not touch high voltage components. If you're unsure, don't touch the component at all. It will not be an enjoyable experience and it will accomplish nothing.

Charged components[edit | edit source]

Components like batteries or capacitors can hold charge despite a device being turned off. Everything in the 'powered components' section above applies to these components as they are effectively still on. Removing batteries is likely possible, but capacitors are trickier.

Capacitors can't hold charge long term like batteries. Most capacitors will discharge after a few seconds if not sooner. Touching the ends of low voltage capacitors with a finger can use your body to safely discharge the capacitor. The danger comes from large high voltage capacitors. Do not touch high voltage capacitors.

Electro-static discharge[edit | edit source]

The human body has the ability to act as a high voltage capacitor an deliver large shocks to electronic components. These shocks aren't large amounts of energy but still have the ability to damage components. Discharging these shocks may result in a light shock or no shock at all.

The solution here is to use an anti-static wrist strap and anti-static mat, with both of these connected to a common ground that connects to an earthed point in your house, or earthed appliance like a desktop computer case. This ensures that the components, you and your environment all share a common voltage level and dissipate capacitance.

Learning and literacy[edit | edit source]

Like mathematics or any abstract medium, electronics is not easily observed by any human sense. It requires an abstract notation to describe and make predictions.

Unfortunately the current notation is heavily visual:

  • Schematics display components and their connections using graphical drawings
  • Signals and behaviour and depicted using two-dimensional graphs
  • Mathematical notation and formulas are used for complex calculations

As far as I know there is no other formal notation for describing electronics than what I've listed above.

The current approach I see is to have a sighted guide handle intake and description of data in to some informal notation.

Tools[edit | edit source]

There are various tools used to investigate and study electronics:

  • Multimeters to measure voltage, resistance and current of a circuit
  • Oscilloscopes to measure voltage waveforms of a circuit
  • Component testers to determine what a component is and its value
  • Electronic design automation software for creating schematics and PCBs
  • Simulators to tests hypothetical circuits

Unfortunately these tools are not accessible to blind folk for a variety of reasons:

  • Physical devices lack braille or audio capabilities
  • Software lacks screen reader support
  • The notation used by software is visual

These aren't entirely unsolvable problems:

  • Some physical devices can be interfaced with a computer and read over USB or a serial port. The open source sigrok project is able to interface with various physical tools and read their displays.
  • Software that lacks screen reader support can in theory be fixed, or alternatives can be developed that use textual descriptions.
  • Notion doesn't exactly matter when dealing with concrete things such as voltage at a location or specific components and simulators are used to experiment.

The current approach I have is to build a basic breadboard multimeter and component tester as well as document how to use things like logic analysers or oscilloscopes with sigrok.

Soldering[edit | edit source]

Soldering is used to create strong electrical connects between components. The idea is simple:

  • Put two electrically conductive surfaces together and heat them
  • Melt a solder alloy over the intersection to create a joint
  • The joint holds the two surfaces together and conducts electricity

Soldering has a long history of being done by the blind. The Smith Kettlewell Technical File and Smith Kettlewell Soldering Basics websites document techniques used to solder without vision.

However these were written in the 1980s and 1990s. These days there's often an added requirement: Components must be placed through small holes on a circuit board, rather than free form. These holes are often placed extremely close together and lack thermal mass. This naturally requires a lot more precision.

Even sighted people have difficulty making these solder joints. It's common for magnifying glasses and microscopes to be used just to verify that joints are correct and functional.

The current approach I've been using is to avoid soldering and focus on solderless techniques such as breadboards. However many components require soldering additional pin headers to be usable with a breadboard, severely limiting the feasibility of this approach.

I fully believe that with the help of some jigs it would be possible to gain the level of precision required to do these joints.

I'm unsure about the solution for soldering smaller surface mount components given there's no tactile indication available that the component is position properly. There are pick and place machines that can solder these components automatically but are very very expensive.

Breadboarding[edit | edit source]

Breadboards are currently the main way to do solderless electronics. It varies by breadboard but generally they contain:

  • A grid of female holes spaced by 2.54mm
  • A series of short metal 'lanes' next to each under the holes, usually with half a dozen holes per lane
  • These lanes grab on to things inserted in to the holes and electrically join them
  • A gap down the middle separating two sets of lanes for inserting components pins on both sides
  • Two very long lanes on each side that run in a different direction to regular lanes, usually used for power
  • These long lanes may be split in to four on some breadboards

There are no tactile hints for which way the lanes run electrically. You can infer the direction as outside the long side lanes for power, lanes are always short not long. If you really want to check you can remove the adhesive backing and feel the metal contacts underneath.

Here's a list of things you might want to make a breadboard electronics project:

  • Resistors
  • Capacitors
  • Diodes
  • Transistors
  • Buttons
  • Buzzers
  • Arduino Micros
  • Multiple breadboards
  • Lots of containers to hold things

You can find a lot of these on sites like Adafruit, SparkFun, and Mouser.

If you're just confused about what to buy, contact me and I can give you some suggestions.

Be sure to check out the Blind Arduino Blog and Blind Arduino mailing list.