I enjoy sitting inside with a glass of wine while imaging. Most of my telescope hardware could be operated remotely. However, some hardware, like the refractor dew strap, the C8 dew heater, the LED flat panel, and a cooling fan, still require manual operation. While commercial switches and PWM controllers are available, they add weight, require more cabling, and are expensive—especially if you're running multiple scopes.
for twelve months i've been designing a small, lightweight, Bluetooth LE-controlled switch (on/off/PWM) that could be plugged "inline" to control all these devices. PWM provides speed control for fans, temperature control for dew heaters and brightness control for flat panels
After two prototypes, it is now complete. I've called it SkySwitch. I've also coded two ASCOM drivers for SkySwitch: a switch driver and a flat panel driver.
I have a few SkySwitches built with 3D printed cases that I would like to distribute for testing.
If you have a Windows-based PC or laptop with Bluetooth (or can attach a Bluetooth dongle) and would like to test a SkySwitch, please PM me.
The following post provides further details and images of the SkySwitch.
You can have multiple SkySwitches connected each with its own configuration.
The Bluetooth connection does not require manual discovery and pairing, all this is handled automatically by the driver.
Only 2 connections, power in and power out.
Reliably handles recovery from any connection loss
Works with any software that uses ASCOM drivers
SkySwitch:
Bluetooth LE 4.0 (FCC certified module)
Red LED status light: flashing is not connected, on is connected
Holds last output value if connection is lost
Operating voltage: 5-18V DC
Current: up to 4A for switch 3A for PWM
Short Duration current up to 7A
Over current protected
Over temperature protected
Short circuit protected
Input polarity protected
Switch output 0 to supply voltage
PWM output 1-2kHz 0-100% duty cycle
KickStart mode: for reliably starting fans
Does not need to be mounted
Weight: 19g
Dimensions: 48x35x17mm
ASCOM SkySwitch Switch Driver
Passes ASCOM conformance tests
Monitors SkySwitch connection and reconnects of connection is lost
If reconnected, reads SkySwitch last output value and displays this
I won't be downgrading to Windows at any time in the foreseeable future.
I was unclear with my words with the "5v/USB" line. I have a dew heater strap that runs from 5v and has a USB-A connector. If you ever design a controller for that type of dew heater I'll be happy to help.
Just letting you it is working with APT! Well, at least it connects - only tested the through power @12v so far and that works. Will test PWM & Panel (if I can figure out something there) soon. I'm guessing multiple switches will show up on the same screen as shown in your N.I.N.A. images when connected?
Another thing I will be testing is the variable power input. Going to try my DSLR @ 9v from as well as other settings available through the variable output from my PPBAv2 - I know you say 5v, but will it go to 3v if needed or won't it even start that low?
It operates just fine at 5v, 7v, 8v, 9v & 12v delivering the correct power throughput.
PWM works fine at 12v - measured by both temperature of a dew strap & voltage throughput (from ~8.5v @ 0% to 12.5v @ 100%).
PWM doesn't seem to like working at 5v. At 0% it outputs ~3.5v but 25%, 50% & 75%, they all output 5.45v which is actually higher than 100% at 5.34v. Note that 1% operates at ~4.9v, but 10% also jumps to 5.45v. Guess I'll have to stick to the low/med/high switch on my USB powered dew straps.
What type of flat panel (cheap) would I need to test SkySwitch in that mode? Any suggestions Chris?
Just letting you it is working with APT! Well, at least it connects - only tested the through power @12v so far and that works. Will test PWM & Panel (if I can figure out something there) soon. I'm guessing multiple switches will show up on the same screen as shown in your N.I.N.A. images when connected?
Another thing I will be testing is the variable power input. Going to try my DSLR @ 9v from as well as other settings available through the variable output from my PPBAv2 - I know you say 5v, but will it go to 3v if needed or won't it even start that low?
Cheers,
Mark
Hi Mark,
Thanks for confirming it works with APT.
Yes, if you're using multiple skyswitch devices the ASCOM driver will detect and display them. I've tested up to 10 switches although it can take up to 5 - 10 seconds for some bluetooth drivers and the OS to connect them after you press connect.
Unfortunately, 3 volts is not possible. The switching highside FET device spec is 4.75v minimum.
It operates just fine at 5v, 7v, 8v, 9v & 12v delivering the correct power throughput.
PWM works fine at 12v - measured by both temperature of a dew strap & voltage throughput (from ~8.5v @ 0% to 12.5v @ 100%).
PWM doesn't seem to like working at 5v. At 0% it outputs ~3.5v but 25%, 50% & 75%, they all output 5.45v which is actually higher than 100% at 5.34v. Note that 1% operates at ~4.9v, but 10% also jumps to 5.45v. Guess I'll have to stick to the low/med/high switch on my USB powered dew straps.
What type of flat panel (cheap) would I need to test SkySwitch in that mode? Any suggestions Chris?
Cheers,
Mark
Hi Mark,
Firstly, you are doing a fantastic (I was tempted to say "stellar") job on this, thank you so much.
I'll do some more testing on the 5V PWM and get back to you on that one.
I think I know what is happening and I'll get back to you with the answer soon.
Can you tell me, are you using a multimeter/voltmeter to test the PWM output or something like an oscilloscope?
I've tested the flat panel drivers with both electroluminescent panels and LED based panels. I can send you a simple 12V LED panel that's about 120mm across if you have a scope around that aperture or less?
Hi Mark,
Firstly, you are doing a fantastic (I was tempted to say "stellar") job on this, thank you so much.
I'll do some more testing on the 5V PWM and get back to you on that one.
I think I know what is happening and I'll get back to you with the answer soon.
Can you tell me, are you using a multimeter/voltmeter to test the PWM output or something like an oscilloscope?
I've tested the flat panel drivers with both electroluminescent panels and LED based panels. I can send you a simple 12V LED panel that's about 120mm across if you have a scope around that aperture or less?
Chris
Hi Chris,
Just using a multimeter to test, don't have anything better. I have a 90mm I could use the LED panel on for testing If you want to send it along.
PWM works fine at 12v - measured by both temperature of a dew strap & voltage throughput (from ~8.5v @ 0% to 12.5v @ 100%).
PWM doesn't seem to like working at 5v. At 0% it outputs ~3.5v but 25%, 50% & 75%, they all output 5.45v which is actually higher than 100% at 5.34v. Note that 1% operates at ~4.9v, but 10% also jumps to 5.45v. Guess I'll have to stick to the low/med/high switch on my USB powered dew straps.
Cheers,
Mark
Hi Mark,
What you have described for the 5V PWM is possibly caused by measuring the output voltage without any device attached. The output +ive pin is floating, that is when nothing is attached to the skyswitch the output pin voltage may float to an undefined voltage. In this case it looks like its showing the FET charge pump voltage which is above the input voltage.
This isn't a problem. When a load is connected it will work correctly and the floating voltage will not cause any problems when a load is attached.
