In the original schematic, I placed 1N5822 Schottky Diodes across each of the dew controller outputs. This was designed to handle any back EMF generated by the long leads of the dew straps. However, the TIP120 transistors have reverse voltage protection already built-in, so in the final version of the schematic I removed the Schottky diodes as I deemed them overkill.
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Hello,
this is a great project and I'm also assembling the focuser one. By the way, in the focuser project I can see a switch and a capacitor between +5v and RST pin in order to do firmware updates. I wonder why this is not implemented in the dew control schema: is it important or redundant?
Thanks in advance and best regards!
Giovanni.
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It can be left out fpor the dew controller. All it does it prevent the controller from doing a reset when an application connects to the controller (and hence the response from the Arduino takes place after the reset is performed, typically 2-3s later). For the focuser this is important for moonlite compatibility.
For the dew controller its not important. I just like to re-use ideas and code across the various projects :-)
Cheers
Robert
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Great, so if one does not use Moonlight focuser it can be left out even from the focuser. Just to my understanding, 5v pin of arduino can be used both to power arduino with 5v external power and for get 5v in case we power arduino from VIN or USB , is it correct?
Cheers,
Giovanni.
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moonlite compatibility not needed - answer is yes the power on reset can be left out as the ASCOM drivers and Windows app wait the necessary 3seconds before attempting to send commands to the controller
Next Question: To power the arduino we either power from USB, when USB is connected, or derive power via VIN.
If powering from USB, limit is less than 200mA total - for everything. This can be restrictive if you try to power transistors and relays and LEDS and a whole bunch of stuff, one can quickly exceed this limit.
Powering from VIn has a number of advantages - first the external supply will probably be able to supply more than 200mA and secondly, it will work even when the USB cable is not connected.
So in our case this is good, because we need more than 200mA and we also want the flexibility of running the controller "in the field" without a computer (in the case of the focuser this would mean the push buttons and LCD are added making the focuser a Full version).
Cheers
Robert.
If you would like to refer to this comment somewhere else in this project, copy and paste the following link:
In the original schematic, I placed 1N5822 Schottky Diodes across each of the dew controller outputs. This was designed to handle any back EMF generated by the long leads of the dew straps. However, the TIP120 transistors have reverse voltage protection already built-in, so in the final version of the schematic I removed the Schottky diodes as I deemed them overkill.
Hello,
this is a great project and I'm also assembling the focuser one. By the way, in the focuser project I can see a switch and a capacitor between +5v and RST pin in order to do firmware updates. I wonder why this is not implemented in the dew control schema: is it important or redundant?
Thanks in advance and best regards!
Giovanni.
It can be left out fpor the dew controller. All it does it prevent the controller from doing a reset when an application connects to the controller (and hence the response from the Arduino takes place after the reset is performed, typically 2-3s later). For the focuser this is important for moonlite compatibility.
For the dew controller its not important. I just like to re-use ideas and code across the various projects :-)
Cheers
Robert
Great, so if one does not use Moonlight focuser it can be left out even from the focuser. Just to my understanding, 5v pin of arduino can be used both to power arduino with 5v external power and for get 5v in case we power arduino from VIN or USB , is it correct?
Cheers,
Giovanni.
moonlite compatibility not needed - answer is yes the power on reset can be left out as the ASCOM drivers and Windows app wait the necessary 3seconds before attempting to send commands to the controller
Next Question: To power the arduino we either power from USB, when USB is connected, or derive power via VIN.
If powering from USB, limit is less than 200mA total - for everything. This can be restrictive if you try to power transistors and relays and LEDS and a whole bunch of stuff, one can quickly exceed this limit.
Powering from VIn has a number of advantages - first the external supply will probably be able to supply more than 200mA and secondly, it will work even when the USB cable is not connected.
So in our case this is good, because we need more than 200mA and we also want the flexibility of running the controller "in the field" without a computer (in the case of the focuser this would mean the push buttons and LCD are added making the focuser a Full version).
Cheers
Robert.