With winter upon us
…it seems more and more people are making unexpected ‘landings’ onto less than desirable ground (or lack thereof!). When this happened to me this weekend on my maiden outing after a re-build I was less than impressed.
Across the internet you will find plenty of information on how to best rescue your drowned electronics. Having attempted a few of these different methods (hair dryers, rice, cat litter, radiator etc..) I have had varied success.
Some of this may be down to the location (i.e. salt water) and some down to the effectiveness of the rescue method but I now follow some basic best practice which has proven effective.. this time at least..
First of all, if you’re going to be at risk of getting wet it is good practice to prepare for the worst. Personally I now coat all my delicate electrical components (ESCS, Flight Control, VTx, PDB) using a varnish, yes the Mrs nail varnish. You can get better stuff such as liquid insulation ‘tape’ however I find nail varnish is cheap, is easy to remove should you need to re-solder anything, is widely available and isn’t toxic.
When the inevitable does happen and you ditch the quad somewhere with excess H20 laying around, disarm immediately, retrieve the quad and un-plug the battery immediately. There is an urge (i know) to power it back up and check for damage but this is the worst thing you could do as any contaminated circuitry could be shorted and destroyed if you put a surge of power through plugging it back in.
Get home, have a cup of tea, warm up and relax. The quad and its electronics shouldn’t sustain any further damage if there is no power. There may be short circuits but with no voltage or current, there’s nothing in the short term to do any damage.
After you have calmed down, start dismantling the quad. I would recommend a full dismantle to be thorough. Take each of the components off, dry them off using kitchen roll or rags and remove any easy to remove dirt. Unsolder any wires, and remove any heat shrink, this will give easy access to clean and treat all the vital components.
.. Not for drinking however, I personally use a can of isopropyl alcohol spray (usually available from electronics stores such as Maplin) which is safe to use on PCBs. The spray can displace water from the PCB (which may not even be visible, i.e. trapped under the processor chip) and also loosen and push clear any other contaminants which you might have picked up.
Taking your time, for each PCB stand it up on its edge and use the straw nozzle with the alcohol spray and work your way from top to bottom with targeted blasts of the spray. Remove any excess alcohol using paper towels, using clean pieces each time as to avoid putting any dirt back onto the board. Pay extra attention around the processor chips and components with tightly spaced pins, work the spray around these to force out any water.
You can see in the photo below the dirt that came out of my ESC just by the pressure of the spray. The dirt wasn’t even visible before!
Note: I would recommend NOT using the alcohol spray on the motors or any parts with bearings as to avoid stripping any lubrication from the part. The motors should not be affected by water contamination as they are just copper coil and magnets. If you need to clean them I suggest dismantling the bell from the stator and using a brush to remove any lodged dirt. If you need to use a little water to help remove the dirt in the motor, I suggest either using distilled water or make sure you thoroughly dry the motor afterwards to avoid corrosion of any steel components.
Don’t forget the bolts/nuts, some are made from steel and can corrode if left wet. I personally remove all bolts, dry them off and then leave them to air for a while. If left screwed in, any trapped water in the thread could leave to corrosion and in the worst case sieze the bolt solid into the part its screwed into.
The final step is to be patient. I know its difficult and you will be eager to check your pride and joy is still functional, however to maximise the chance of rescuing the quad leave it at least overnight and preferably even longer (a couple of days or more) somewhere warm. I stuck mine on the radiator for the day. This will be our last ditch attempt to make sure any remaining water is removed.
Test & Reassemble
Finally you have done all the steps to maximise the chance of saving the quad / components. One component at a time, wire it up on the bench and power it up to check if it works. Take caution here, there is a chance it did not work and the component might in the worst case go up in smoke or even fire. Just be ready!
For a PDB, power it up without any components connected and run a voltage meter across the terminals to check the power output is as expected (i.e. from the regulators). I have had faulty PDBs after water damage outputting incorrect voltage going unnoticed and damaging other components I connected to it.
That’s all folks. I hope this read has helped somewhat or at least has been interesting. In this occasion I was lucky and all components survived the splash.