Date   
Re: Question about dew heater control.

Howard Dutton
 
Edited

The Aux4 pin doesn't seem to support pwm on the STM32.

Re: Question about dew heater control.

Howard Dutton
 

With this installed you should be able to compile with the reticle OFF and also the home switches OFF and send the following command to turn the reticle output on/off (HIGH/LOW.)

:SXG3,0#
:SXG3,1#

Aux3 can be set for pwm mode in the pin-map (disabled by default) or this line in Config.h:
#define Aux3_Analog

Then for off, 50%, 100%:
:SXG3,0#
:SXG3,127#
:SXG3,255#

Re: Question about dew heater control.

Howard Dutton
 

I updated the master branch OnStep STM32 pin-map:

I cleaned up the STM32 pin-map file again.  Please compare it methodically to the prior version to be sure I have all of the pins assigned properly and/or test carefully!
I don't have the STM32 board installed at the moment so can't even check to see if it will compile.

I also set things up so:

The Reticle pin is now bound to Aux3.
The PPS pin is now bound to Aux4.
Aux3/4 optionally supports Home Switches.
Aux4 optionally supports OneWire devices.

Validation should flag down invalid uses of these just is it does for other pin-maps.  For example, turn on the DS1820 and enable the PPS option and it should #error on compilation.

Re: Showcase: Built With OnStep

Roman Hujer
 

My new adaptation EQ5 (SkyWatcher) telescope mount to OnStep https://www.thingiverse.com/thing:4170058 Roman

Re: Question about dew heater control.

Aisling Lightworks
 

With millis()

Re: Question about dew heater control.

Serge CLAUS
 

Hello,
You can make a mini Shield with a MOSFET which plugs in place of a stepper module and which is controlled by step or dir.


Le 20 février 2020 20:26:45 GMT+01:00, "Jerry via Groups.Io" <jerry.biehler@...> a écrit :
Yeah. I think something that just connects to one of the aux io. Especially the DB9 on Max since that’s where the temp sensor connects anyway. 

-Jerry

On Feb 20, 2020, at 11:24 AM, Howard Dutton via Groups.Io <hjd1964@...> wrote:

On Thu, Feb 20, 2020 at 11:09 AM, Jerry wrote:
I’m not sure using stepper drivers will work well. You would have to control with the direction line and I am not sure if that has any effect on the output until there is a direction change. It’s too much of an unknown on what’s going on with an output when you could just drive a SSR. You could also use one of my line driver boards to drive two heater SSRs
This isn't to say I'm convinced it should be done, those outputs are for focuser/rotator motors, feels like a hack.

And the whole thing adds serious additional power requirements.to the controller.

When it comes down to it this is something I always imagined plugging into the DB9 on the MaxPCB2 and where it had its own dedicated power supply/connectors.

--
Envoyé de mon appareil Android avec Courriel K-9 Mail. Veuillez excuser ma brièveté.

Re: Question about dew heater control.

Aisling Lightworks
 

My dew heaters have their own regulated power supply that limits their Max wattage. I think I'll just hack the reticle pin to flip a relay on and off for a given percentage of the time with a timer loop.

Re: Question about dew heater control.

Jerry
 

Yeah. I think something that just connects to one of the aux io. Especially the DB9 on Max since that’s where the temp sensor connects anyway. 

-Jerry

On Feb 20, 2020, at 11:24 AM, Howard Dutton via Groups.Io <hjd1964@...> wrote:

On Thu, Feb 20, 2020 at 11:09 AM, Jerry wrote:
I’m not sure using stepper drivers will work well. You would have to control with the direction line and I am not sure if that has any effect on the output until there is a direction change. It’s too much of an unknown on what’s going on with an output when you could just drive a SSR. You could also use one of my line driver boards to drive two heater SSRs
This isn't to say I'm convinced it should be done, those outputs are for focuser/rotator motors, feels like a hack.

And the whole thing adds serious additional power requirements.to the controller.

When it comes down to it this is something I always imagined plugging into the DB9 on the MaxPCB2 and where it had its own dedicated power supply/connectors.

Re: Question about dew heater control.

Howard Dutton
 

On Thu, Feb 20, 2020 at 11:09 AM, Jerry wrote:
I’m not sure using stepper drivers will work well. You would have to control with the direction line and I am not sure if that has any effect on the output until there is a direction change. It’s too much of an unknown on what’s going on with an output when you could just drive a SSR. You could also use one of my line driver boards to drive two heater SSRs
This isn't to say I'm convinced it should be done, those outputs are for focuser/rotator motors, feels like a hack.

And the whole thing adds serious additional power requirements.to the controller.

When it comes down to it this is something I always imagined plugging into the DB9 on the MaxPCB2 and where it had its own dedicated power supply/connectors.

Arduino Mega-WiFi a better solution than the MKS Gen-L card?

Serge CLAUS
 

Hello,
I am using an MKS Gen-L card for OnStep.
I also have an Arduino Mega-WiFi board from RobotDyn.
It is an Arduino Mega with an ESP8266 integrated into the board.
I see several advantages:
- A more compact format (but thicker with the Ramps card).
- No Wemos connection, the ESP is already integrated. It communicates by Serial3 with the arduino.
- I2c Pins are available.
- No additional component on the serial ports which all become usable.
- The ATMEGA also has a 16MHZ quartz unlike the "normal" Arduino Mega
- It is possible to use an intermediate shield for bluetooth, RTC ...

Re: Question about dew heater control.

Howard Dutton
 

On Thu, Feb 20, 2020 at 11:09 AM, Jerry wrote:
You would have to control with the direction line and I am not sure if that has any effect on the output until there is a direction change.
It does.

It’s too much of an unknown on what’s going on with an output when you could just drive a SSR.
If I can run decent size DC motors on it and they can heat the heck out of a stepper motor it's not much of an unknown.

Re: Question about dew heater control.

Howard Dutton
 

On Thu, Feb 20, 2020 at 10:53 AM, Howard Dutton wrote:
You could drive up to ~2A per coil with a DRV8825 this way though you will probably want something other than an RJ connector in this application.
And you'll want to confirm the PCB design is up for handling that too.

My designs were built for lower power stepper motors intended for focuser/rotator operation.  You would have to omit the 12V regulator and bridge, then for example running at 24VDC, you could pull about an 1A @ 24V so about 24 watts maximum.

Re: Question about dew heater control.

Jerry
 

I’m not sure using stepper drivers will work well. You would have to control with the direction line and I am not sure if that has any effect on the output until there is a direction change. It’s too much of an unknown on what’s going on with an output when you could just drive a SSR. You could also use one of my line driver boards to drive two heater SSRs

BTW, is there a way to access the DS1820 temp? I hooked one up and would like to see if it is working. 

-Jerry

On Feb 20, 2020, at 10:57 AM, Howard Dutton via Groups.Io <hjd1964@...> wrote:

On Thu, Feb 20, 2020 at 10:45 AM, Howard Dutton wrote:
On Thu, Feb 20, 2020 at 10:36 AM, Jerry wrote:
Most PID controllers for heaters cycle on/off at anywhere from 1 second to 5 seconds. On old mechanical relay systems that was even slower to help eliminate contact wear. PWM is just not necessary with the thermal mass that is being driven
Very true.  We don't want to be making any more RFI than necessary too.
Perhaps the only problem with this is when the heater element design is such that throttling is required otherwise excessive heating will occur in a very short amount of time.

Re: Question about dew heater control.

Howard Dutton
 
Edited

On Thu, Feb 20, 2020 at 10:45 AM, Howard Dutton wrote:
On Thu, Feb 20, 2020 at 10:36 AM, Jerry wrote:
Most PID controllers for heaters cycle on/off at anywhere from 1 second to 5 seconds. On old mechanical relay systems that was even slower to help eliminate contact wear. PWM is just not necessary with the thermal mass that is being driven
Very true.  We don't want to be making any more RFI than necessary too.
Perhaps the only problem with this is when the heater element design is such that fast pwm is required otherwise excessive heating will occur in a very short amount of time.

A stepper driver's Vref setting can take care of this though the one setting applies to both outputs.

Re: Question about dew heater control.

Howard Dutton
 

On Thu, Feb 20, 2020 at 09:52 AM, Aisling Lightworks wrote:
Good thinking. Doesn't need to go on and off that quickly. A simple timer on and off loop.
I checked/thought about it...

Pretty sure you can drive two heater elements from one A4988 or DRV8825 stepper driver.

Half-step mode allows you to turn ON: Coil A OR Coil B OR Coil A and B.  Use the Enable signal to turn both Coil A and B OFF.  So any combination of ON/OFF states can be set.  This will be a little complicated to program but easier than the DC focuser stuff.

You could drive up to ~2A per coil with a DRV8825 this way though you will probably want something other than an RJ connector in this application.

Re: Question about dew heater control.

Howard Dutton
 
Edited

On Thu, Feb 20, 2020 at 10:36 AM, Jerry wrote:
Most PID controllers for heaters cycle on/off at anywhere from 1 second to 5 seconds. On old mechanical relay systems that was even slower to help eliminate contact wear. PWM is just not necessary with the thermal mass that is being driven
Very true.  We don't want to be making any more RFI than necessary too.

Just send the commands from the WiFi Addon to turn the heaters on/off and have it handle the timing.

Re: Question about dew heater control.

Jerry
 

Most PID controllers for heaters cycle on/off at anywhere from 1 second to 5 seconds. On old mechanical relay systems that was even slower to help eliminate contact wear. PWM is just not necessary with the thermal mass that is being driven. 

-Jerry

On Feb 20, 2020, at 10:24 AM, Serge CLAUS <serge@...> wrote:



Hello,

I'm using a dew-heater system controlled by the mosfet of the MKS Gen-L card.
I modified the OnStep program version 2.x to control the heating according to the temperature of the secondary mirror.
The secondary mirror temperature is given by the DS18S20 and I use the dew point temperature to control the heater.
On the other hand, it seems to me that on version 3.x that the focuser uses the DS18S20 to correct the focus.

https://github.com/plop3/OnStep

Translated with www.DeepL.com/Translator (free version)

Le 20/02/2020 à 18:52, Aisling Lightworks a écrit :
Good thinking. Doesn't need to go on and off that quickly. A simple timer on and off loop.

Re: Question about dew heater control.

Howard Dutton
 

On Thu, Feb 20, 2020 at 09:52 AM, Aisling Lightworks wrote:
Good thinking. Doesn't need to go on and off that quickly. A simple timer on and off loop.
Agree.

With my DC motor control from what I recall, and it's been a while:
  • For the DRV8825 and A4988
  • PWM is done with the driver ENable signal.
  • The stepper driver gets set to half-stepping mode (shunts.)
  • My OnStep advances the step position such that only one coil set (A or B) is energized in either the forward or reverse direction.  The other coil set is idle (not driving a current.)  This allows me to select either A or B coils and drive two DC motors (but only one at a time.)
Good review for me I was (and still am) struggling to remember the details of DC motor control for filling in the Config.h Wiki section.

Re: Question about dew heater control.

Serge CLAUS
 

Hello,

I'm using a dew-heater system controlled by the mosfet of the MKS Gen-L card.
I modified the OnStep program version 2.x to control the heating according to the temperature of the secondary mirror.
The secondary mirror temperature is given by the DS18S20 and I use the dew point temperature to control the heater.
On the other hand, it seems to me that on version 3.x that the focuser uses the DS18S20 to correct the focus.

https://github.com/plop3/OnStep

Translated with www.DeepL.com/Translator (free version)

Le 20/02/2020 à 18:52, Aisling Lightworks a écrit :
Good thinking. Doesn't need to go on and off that quickly. A simple timer on and off loop.

Re: Question about dew heater control.

Aisling Lightworks
 

Good thinking. Doesn't need to go on and off that quickly. A simple timer on and off loop.