Outdoor long term test


Chad Gray
 

I have had this OnStep MiniESP outside in Ohio weather for more than a year.  So we get hot humid in the summer and cold/snow in the winter.  no salt water near by.  I use a TeleGizmos 365 scope cover on my mount.

I have found corrosion on the ESP 8266.  A simple dab of oil would probably be the best preventer on these laser etched metal bits.

I will be taking the entire thing apart to see if green crusties have grown anywhere.  The unit functions perfectly still.  I do wonder about the pots on the drivers.  Seems like a good place to have a problem.




--
Authorized OnStep Dealer and Creator of the CGE Pro Conversion Kit
https://graydigitalarts.com/


adraasch
 

To avoid such reliability nightmares, you might consider using conformal coating products like this:

Apply the coating with new parts, after you have fully proven your configuration.

Alternatively, or possibly in addition to consider a small heater in the enclosure which can be enabled when the local conditions are close to the dew point or sometimes in Ohio, frost point.

A ten watt power resistor with a value selected that it would dissipate five watts at whatever supply voltage you are using for motor drive would keep the electronics warm enough that condensation should not form inside a plastic enclosure.

In a former job I worked on printed circuit boards that needed to operate in very hostile environments with high voltage.  They were high intensity strobe light control boards for use on tall towers.  We used conformal coating to protect the boards from condensation which would lead to arcing and board failure.  These boards were also exposed to high levels of ozone, the coatings protected the components from that as well.  The boards initially had dip switches to configure board address parameters, we tried the best we could find, with protective covers.  They still failed.  We eventually used jumper wires which were then conformal coated.

These boards were installed in metal enclosures which did have heaters, but given that the enclosures were often enveloped in clouds, rain, snow, sleet, etc. you could expect that some moisture would form inside the enclosures.  Thus the need for the conformal coatings.

As for the pot on the stepper drivers, you have identified a weak point from a reliability standpoint.  This likely would be just fine inside a 3D printer in an office environment, but not so good in harsh environments.  If this pot gets noisy, it could lead to intermittent drive failures where not enough current is supplied to the motors, or worse yet, too much and the motors are permanently damaged.

Some drivers can be configured to ignore the pot setting.  Another solution for those with soldering skills on SMT boards would be to remove the pot and replace it with two resistors which are selected to provide the same voltage at the "wiper" connection as the pot did, then conformally coat the entire lot.

IC sockets are also a weak point, are all the sockets and headers used gold plated?  Gold resists corrosion, is very ductile, and highly conductive.  As boards cycle in temperature they expand and contract.  This applies stresses to IC sockets which can cause temperature driven intermittents.  These are real fun to troubleshoot.  From a reliability standpoint, eliminating as many sockets in a design as possible is preferred as these are known failure points in harsh environments.

A word of caution regarding conformal coatings and socketed parts is probably in order.  Once coated, if you need to remove a driver or module from a socket the coating needs to be stripped from the pins on the driver or module, and the socket should be replaced with a new one.  If you don't do this, you might find that the conformal coating could cause intermittent connections in the old socket.

Hope this helps,

Arlen

On Fri, Dec 2, 2022 at 9:57 AM Chad Gray <rchadgray@...> wrote:
I have had this OnStep MiniESP outside in Ohio weather for more than a year.  So we get hot humid in the summer and cold/snow in the winter.  no salt water near by.  I use a TeleGizmos 365 scope cover on my mount.

I have found corrosion on the ESP 8266.  A simple dab of oil would probably be the best preventer on these laser etched metal bits.

I will be taking the entire thing apart to see if green crusties have grown anywhere.  The unit functions perfectly still.  I do wonder about the pots on the drivers.  Seems like a good place to have a problem.




--
Authorized OnStep Dealer and Creator of the CGE Pro Conversion Kit
https://graydigitalarts.com/


Chad Gray
 

Awesome information Arlen!  Thanks!  That is a lot to think about.

My CGE Pro kit i have been soldering the bits straight to the PCB to avoid weak spots.  I have optimized the design to the point where i dont find replacing a part vs. the entire PCB to be worth it.  So i have started treating the entire PCB as the replacement if something goes wrong.

I knew about conformal fluid, but I have been hesitant to use it.  

Great idea on the POT!  My LV8729 i tend to run wide open on 2amp Nema17's.  So I could just run then shorted.

Interesting idea on a "dew heater" for the OnStep computer enclosure.  :)

Chad


On Fri, Dec 2, 2022 at 10:44 AM adraasch <araasch@...> wrote:
To avoid such reliability nightmares, you might consider using conformal coating products like this:

Apply the coating with new parts, after you have fully proven your configuration.

Alternatively, or possibly in addition to consider a small heater in the enclosure which can be enabled when the local conditions are close to the dew point or sometimes in Ohio, frost point.

A ten watt power resistor with a value selected that it would dissipate five watts at whatever supply voltage you are using for motor drive would keep the electronics warm enough that condensation should not form inside a plastic enclosure.

In a former job I worked on printed circuit boards that needed to operate in very hostile environments with high voltage.  They were high intensity strobe light control boards for use on tall towers.  We used conformal coating to protect the boards from condensation which would lead to arcing and board failure.  These boards were also exposed to high levels of ozone, the coatings protected the components from that as well.  The boards initially had dip switches to configure board address parameters, we tried the best we could find, with protective covers.  They still failed.  We eventually used jumper wires which were then conformal coated.

These boards were installed in metal enclosures which did have heaters, but given that the enclosures were often enveloped in clouds, rain, snow, sleet, etc. you could expect that some moisture would form inside the enclosures.  Thus the need for the conformal coatings.

As for the pot on the stepper drivers, you have identified a weak point from a reliability standpoint.  This likely would be just fine inside a 3D printer in an office environment, but not so good in harsh environments.  If this pot gets noisy, it could lead to intermittent drive failures where not enough current is supplied to the motors, or worse yet, too much and the motors are permanently damaged.

Some drivers can be configured to ignore the pot setting.  Another solution for those with soldering skills on SMT boards would be to remove the pot and replace it with two resistors which are selected to provide the same voltage at the "wiper" connection as the pot did, then conformally coat the entire lot.

IC sockets are also a weak point, are all the sockets and headers used gold plated?  Gold resists corrosion, is very ductile, and highly conductive.  As boards cycle in temperature they expand and contract.  This applies stresses to IC sockets which can cause temperature driven intermittents.  These are real fun to troubleshoot.  From a reliability standpoint, eliminating as many sockets in a design as possible is preferred as these are known failure points in harsh environments.

A word of caution regarding conformal coatings and socketed parts is probably in order.  Once coated, if you need to remove a driver or module from a socket the coating needs to be stripped from the pins on the driver or module, and the socket should be replaced with a new one.  If you don't do this, you might find that the conformal coating could cause intermittent connections in the old socket.

Hope this helps,

Arlen

On Fri, Dec 2, 2022 at 9:57 AM Chad Gray <rchadgray@...> wrote:
I have had this OnStep MiniESP outside in Ohio weather for more than a year.  So we get hot humid in the summer and cold/snow in the winter.  no salt water near by.  I use a TeleGizmos 365 scope cover on my mount.

I have found corrosion on the ESP 8266.  A simple dab of oil would probably be the best preventer on these laser etched metal bits.

I will be taking the entire thing apart to see if green crusties have grown anywhere.  The unit functions perfectly still.  I do wonder about the pots on the drivers.  Seems like a good place to have a problem.




--
Authorized OnStep Dealer and Creator of the CGE Pro Conversion Kit
https://graydigitalarts.com/


--
Authorized OnStep Dealer and Creator of the CGE Pro Conversion Kit
https://graydigitalarts.com/


Howard Dutton
 
Edited

On Fri, Dec 2, 2022 at 07:44 AM, adraasch wrote:
As for the pot on the stepper drivers, you have identified a weak point from a reliability standpoint.  This likely would be just fine inside a 3D printer in an office environment, but not so good in harsh environments.  If this pot gets noisy, it could lead to intermittent drive failures where not enough current is supplied to the motors, or worse yet, too much and the motors are permanently damaged.
FYSETC E4 should be a good option as there are no pots on the drivers, and the drivers are integrated on the PCB.


adraasch
 

Chad,

Another thing to consider is the placement of connectors on controllers that are meant to be left outside for extended periods of time.

Enclosures with connectors on multiple sides/ends are difficult to protect from water ingress.

All the connections should leave from the bottom of the enclosure.  If any displays are in the design and they must be on the top or the front side to be visible, use a gasketed seal over all LEDs and displays.  This allows one to mount the enclosure so the connections are leaving the enclosure from the bottom and any condensation / moisture / rain will tend to drip away from instead of enter into the enclosure.  Seal the enclosure tightly but have a single weap hole in the lowest point of the enclosure.  Cover the weap hole with an air permeable membrane to prevent insects from plugging the hole.  One source of such a membrane is from inside a discarded magnetic hard drive, this filtered the particles from the air inside the computer while allowing the air pressure inside the enclosure to equalize as the atmospheric pressure changed or the drive temperature changed.  Look for a small hole on the outside of the hard drive enclosure where the rotating disk pack is located, the membrane/filter will be under that hole.  If you glue the filter/membrane to the outside of the bottom of the enclosure over a small hole, insects will not be tempted to plug the hole as they can't see it.  To seal a plastic case that has a lid or end caps, consider painting the case with multiple coats of acrylic paint once you are certain you won't need to get inside the case for a while.  Cover the weap hole membrane temporarily with tape to prevent sealing that.  Use a paint that is listed for outdoor use as it will have UV resistant properties and won't discolor as much over time.

All cables leaving the controller should have a drip loop, I.E. should first go straight down, then curve upwards toward the mount and telescope.  This allows any moisture that forms on the cable jackets to drip harmlessly from the cable jacket instead of following the cable jacket to the connector to the controller.

So, what to do if you have a design that has cables leaving from all sides and you don't want to redesign it?  Make water-tight plastic enclosure that is open on the bottom that the entire controller can fit inside with its cables connected.  Still use drip loops on all the cables.  If the enclosure is clear you can still see the display.  A hinged, gasketed front cover could be made with magnets to hold the cover closed if you needed access to the controller to set switches/or connect cables.

One more word on LEDs.  Often LEDs are driven directly from microcontroller GPIO lines.  These same LEDs are then often installed on the outside of an enclosure so the end user can see the status of the device.  Something often overlooked is the risk to such a design from damage by electrostatic discharge.  If you walk up to your controller in dry conditions you may have a charge on your body of 100Kv or more.  Touch the LED, and a static discharge may occur and be routed to the microcontroller GPIO pin.  Whether or not the pin fails to operate, the microcontroller enters a soft fail state, or a hard fail state is anyone's guess.

Commercial designs avoid this by using light pipes on status LEDs.  Look carefully on Ethernet connectors with activity indicator LEDs.  You will see SMT LEDs on a PCB with acrylic light pipes bringing the LED's light out to the rear of the connector.  Same for cable modems, printers, etc.  This simplifies the assembly of the device while avoiding ESD damage.

DIY'ers can make their own acrylic light pipes by cutting acrylic rod and polishing the ends.  If you want to make lots, you can make a silicone mold and cast them yourself in any shape you need.

You could alternatively provide ESD protection circuitry on the LED lines(s).

Hope this helps,

Arlen  

On Fri, Dec 2, 2022 at 11:23 AM Chad Gray <rchadgray@...> wrote:
Awesome information Arlen!  Thanks!  That is a lot to think about.

My CGE Pro kit i have been soldering the bits straight to the PCB to avoid weak spots.  I have optimized the design to the point where i dont find replacing a part vs. the entire PCB to be worth it.  So i have started treating the entire PCB as the replacement if something goes wrong.

I knew about conformal fluid, but I have been hesitant to use it.  

Great idea on the POT!  My LV8729 i tend to run wide open on 2amp Nema17's.  So I could just run then shorted.

Interesting idea on a "dew heater" for the OnStep computer enclosure.  :)

Chad


On Fri, Dec 2, 2022 at 10:44 AM adraasch <araasch@...> wrote:
To avoid such reliability nightmares, you might consider using conformal coating products like this:

Apply the coating with new parts, after you have fully proven your configuration.

Alternatively, or possibly in addition to consider a small heater in the enclosure which can be enabled when the local conditions are close to the dew point or sometimes in Ohio, frost point.

A ten watt power resistor with a value selected that it would dissipate five watts at whatever supply voltage you are using for motor drive would keep the electronics warm enough that condensation should not form inside a plastic enclosure.

In a former job I worked on printed circuit boards that needed to operate in very hostile environments with high voltage.  They were high intensity strobe light control boards for use on tall towers.  We used conformal coating to protect the boards from condensation which would lead to arcing and board failure.  These boards were also exposed to high levels of ozone, the coatings protected the components from that as well.  The boards initially had dip switches to configure board address parameters, we tried the best we could find, with protective covers.  They still failed.  We eventually used jumper wires which were then conformal coated.

These boards were installed in metal enclosures which did have heaters, but given that the enclosures were often enveloped in clouds, rain, snow, sleet, etc. you could expect that some moisture would form inside the enclosures.  Thus the need for the conformal coatings.

As for the pot on the stepper drivers, you have identified a weak point from a reliability standpoint.  This likely would be just fine inside a 3D printer in an office environment, but not so good in harsh environments.  If this pot gets noisy, it could lead to intermittent drive failures where not enough current is supplied to the motors, or worse yet, too much and the motors are permanently damaged.

Some drivers can be configured to ignore the pot setting.  Another solution for those with soldering skills on SMT boards would be to remove the pot and replace it with two resistors which are selected to provide the same voltage at the "wiper" connection as the pot did, then conformally coat the entire lot.

IC sockets are also a weak point, are all the sockets and headers used gold plated?  Gold resists corrosion, is very ductile, and highly conductive.  As boards cycle in temperature they expand and contract.  This applies stresses to IC sockets which can cause temperature driven intermittents.  These are real fun to troubleshoot.  From a reliability standpoint, eliminating as many sockets in a design as possible is preferred as these are known failure points in harsh environments.

A word of caution regarding conformal coatings and socketed parts is probably in order.  Once coated, if you need to remove a driver or module from a socket the coating needs to be stripped from the pins on the driver or module, and the socket should be replaced with a new one.  If you don't do this, you might find that the conformal coating could cause intermittent connections in the old socket.

Hope this helps,

Arlen

On Fri, Dec 2, 2022 at 9:57 AM Chad Gray <rchadgray@...> wrote:
I have had this OnStep MiniESP outside in Ohio weather for more than a year.  So we get hot humid in the summer and cold/snow in the winter.  no salt water near by.  I use a TeleGizmos 365 scope cover on my mount.

I have found corrosion on the ESP 8266.  A simple dab of oil would probably be the best preventer on these laser etched metal bits.

I will be taking the entire thing apart to see if green crusties have grown anywhere.  The unit functions perfectly still.  I do wonder about the pots on the drivers.  Seems like a good place to have a problem.




--
Authorized OnStep Dealer and Creator of the CGE Pro Conversion Kit
https://graydigitalarts.com/


--
Authorized OnStep Dealer and Creator of the CGE Pro Conversion Kit
https://graydigitalarts.com/