318 replies to this topic

[fmendes]

Yes, that covers how to ADD one channel of smart dew control to the HBG3.  You'll also need to build the HBG3 itself.  See here:

 

https://rtr.ca/hbg3/

https://rtr.ca/hbg3/assembly/

 

Cheers
 

 

Thank you! I'll send you a PM for a kit (if you have) or the PCB.

 

 

Welcome to this thread!

 

I know there is a lot of stuff here but you might start at Post # 162...

 

https://www.cloudyni...rol/?p=13177277

 

That post shows the updated circuit and all necessary connections.

 

Cheers.

 

I saw this schematic, but I'm still in the dark about how to connect the ADS1115.

 

One more question, what about this ESP32 board? It already has a 128x64 display. Just not red, but I can put some red gel in front. Connects to pins SDA and SCL.

https://www.amazon.c.../dp/B0CN4F354N/

Edited by fmendes, 05 June 2024 - 05:25 PM.

[mlord]

Information about building the HBG3 itself, and the exact parts required, is all at https://rtr.ca/hbg3/

Any substitutions, such as different ESP32 boards, are NOT going to work.

 

Cheers

[mlord]

I saw this schematic, but I'm still in the dark about how to connect the ADS1115.

 

Ah yes, it is very very simple, and many people will figure it out.  But a nice updated wiring diagram would also be a great idea.  I'll put it on my list for later, unless someone else here beats me to it!

 

Cheers

[fmendes]

Deleted. I'll work it again on your instructions tomorrow.

Edited by fmendes, 05 June 2024 - 11:23 PM.

[mlord]

No, not correct.  Please DELETE that wiring diagram!

 

The big error is the wire from the right-hand side of the resistor must instead continue to go to 3.3V.

But the other side of the resistor, GREEN, should go to A1 on the ADS1115, instead of to THM0 on the HBG3.

 

So, delete that diagram, and post a corrected version if you can.

Otherwise, I'll work something up in a day or so.

Edited by mlord, 05 June 2024 - 08:28 PM.

[fmendes]

Still busy with life. Hopefully on the weekend.

[mlord]

Local Star Party nearby here last night, so I took the rig and used it outdoors for the first time in 2024!

 

The Auto Smart Dew Control was not working for me -- to be investigated/fixed today soon -- but Manual mode was fine.

Edited by mlord, 16 June 2024 - 11:53 AM.

[mlord]

The Auto Smart Dew Control was not working for me -- to be investigated/fixed today soon -- but Manual mode was fine.

Everything looks normal indoors in a calmer situation than at the Star Party.  So, nothing obvious for me to fix just yet.  I'll get the rig outdoors next available opportunity and pay closer attention to it then.

 

Cheers
 

[mlord]

For building this project, one may still follow the original design, shown in this post:  https://www.cloudyni...7#entry13177277

 

 

But here (below) is the updated wiring diagram, showing two channels of Dew Control, along with a very accurate ADS1115 module for measuring the thermistor temperatures:

 

Click on the image above for a larger, clearer version for printing.

 

I employ 10K-ohm resistors with 0.1% tolerance for use with the thermistors.  1.0% would  probably be fine, but the run of the mill ones are normally only 5% tolerance, which can affect temperature readings.

 

Thermistors don't have a polarity, so their two wires can connect either way around.  This includes the thermistors built-into the Celestron Dew Heater Rings.

 

Ditto for the Dew Heater outputs:  The red/green wiring can be connected either way around to those as well.  But for safety, I would normally connect the red wire to the inside of any connector, rather than the more exposed outside.

 

This arrangement also includes two, optional resistors:  30K-ohms and 10K-ohms, used for measuring the actual "+12V" input voltage to the Dew Heaters.  These should also be at least 1.0% tolerance. This reading will (eventually) be made available to CPWI and the Nexstar+ hand-controllers, but I have yet to add code for it to the firmware.  Real Soon Now.    Those two resistors can be anything 10K or larger, so long as the ratio between them is 3:1.  I suggest using three 10K resistors in series as the "30K" resistor, and then another single 10K with that -- saves having to acquire multiple different ones, especially if they're from the same bag as the ones used with the thermistors!

 

The 3V3 and GND connections to the HBG3 PCB can go to any pads on that PCB which are labelled as 3V3 or GND.  In particular, you will find it more convenient to use the I2C pads for those.  I didn't draw it that way, simply because it might be too cluttered to read if I had. 

 

If one requires only a single channel of smart dew control, then simply omit Thermistor-1, its resistor, and the LR7843 module shown below it.

 

If pure manual dew control is all that's needed, then omit the SHT30 module, and set dew.force.enabled to true on the HBG3 Serial/Debug interface:

 

   set dew.force.enabled true

   save

   reset

 

If trying to wire this alongside the HBG3 Relay PCB, my advice is:  don't do it!!     It is possible, but it gets messy, due to pin conflicts on the HBG3 that require wiring things slightly differently than shown above.  Move the PWM line for the first channel to ESP32 pin 12, and move the PWM line for the second channel to ESP32 pin 18.  If the ADS1115 is omitted, then also move the Thermistor-0 line to ESP32 pin 36.

 

Cheers

Edited by mlord, 25 June 2024 - 08:57 PM.

[mlord]

Thermistors don't have a polarity, so their two wires can connect either way around.  This includes the thermistors built-into the Celestron Dew Heater Rings.

At the time of writing, I had not actually tested that feature.  It turns out that it requires one additional connection, joining the GND from the Dew Heater power supply to that of the HBG3.

 

So the diagram in the above post has now been updated (again!) showing that extra black GND-to-GND wire.

 

Cheers

[mlord]

This arrangement also includes two, optional resistors:  30K-ohms and 10K-ohms, used for measuring the actual "+12V" input voltage to the Dew Heaters. ... It turns out that it requires one additional connection, joining the GND from the Dew Heater power supply to that of the HBG3.

I have not yet released updated code to read/report the Dew Control voltage, because I am still debugging an unexpected interaction somewhere in my setup which causes the thermistor readings to be WAY off when 12V Dew power is connected.

 

If I cut the connection from the 12V Dew Control voltage to the 30K resistor, everything reverts back to normal again.  But of course, with that done the circuit can no longer measure/report the 12V Dew Control voltage.

 

So.. unless one of the hardware geeks here chips in and and figures out why this happens, and how to fix it, I will instead have to publish an updated wiring diagram again, without the 30K+10K resistors for measuring the voltage.  C'est la vie.

 

Cheers

Edited by mlord, 11 July 2024 - 10:05 PM.

[scopewizard]

I have not yet released updated code to read/report the Dew Control voltage, because I am still debugging an unexpected interaction somewhere in my setup which causes the thermistor readings to be WAY off when 12V Dew power is connected.

 

If I cut the connection from the 12V Dew Control voltage to the 30K resistor, everything reverts back to normal again.  But of course, with that done the circuit can no longer measure/report the 12V Dew Control voltage.

 

So.. unless one of the hardware geeks here chips in and and figures out why this happens, and how to fix it, I will instead have to publish an updated wiring diagram again, without the 30K+10K resistors for measuring the voltage.  C'est la vie.

 

Cheers

30k/10k reports 4v to the pin, you are exceeding the 3.5v max, I use 30k and 7.5k which work fine.

[mlord]

12V / 4 = 3.0V to the pin.  Less than the Vcc (3.3V) limit.

 

Should be okay.  The circuit does accurately measure the 12.38V input I'm using, but at the expense of the thermistors not reading accurately.  I can try the 5:1 ratio you have though.

 

Does your set-up use the same ADS1115 for the voltage measurement as for thermistor readings?

[scopewizard]

Does your set-up use the same ADS1115 for the voltage measurement as for thermistor readings?

Yes it does.

[mlord]

Okay.  The ADS1115 datasheet does say something about really high impedance not being good, but I've forgotten what exactly (EDIT: that's more for very large M-Ohm resistances).  So.. on a breadboard here now, I have an HBG3 plugged to another ADS1115, with a thermistor wired, and a 20K/5K divider for the 12.38V power supply.

 

The 12.38V is reading high, showing 12.56V most of the time, and that's with measured resistors and their actual values plugged into the formula.

 

The thermistor is not affected by the 12V supply on this breadboard version.  So it could be the resistances I initially used were too high, or something else.  I'll find out when I swap the resistors in my main unit later on.

 

Thanks.

Edited by mlord, 13 July 2024 - 07:59 AM.

[scopewizard]

Mark,

 

The 20k/5k is a 4:1 ratio same as 30k/7.5k which put the voltage to the ADS1115 at >3.5v, Gain 4096 is max 4.0v.

This also allow reading voltages up to 15v.

Some LiFePO4 battery can read as high as 14.6v.

I have tested my ADS1115 on a few channels with higher than 4.0v (gain 4096)  and the units causes error on other channels.

Edited by scopewizard, 12 July 2024 - 04:07 PM.

[mlord]

Think again!    20+5K is a 5:1, not 4:1.

It's (20 + 5) : 5, which is 5:1. 

Edited by mlord, 13 July 2024 - 07:33 AM.

[scopewizard]

I wrote 20k/5k (20k divided by 5k) 4 part to 1 part feed to the ADS1115.

 

Yes the total is 5 to return it to input voltage.

 

The resistors are not dead on so adjustments are  needed to true value (ohm meter), (r1+r2) / r1

[scopewizard]

That's the odd thing.  I've measured the pair of resistors, and am using their measured values in the calculation.  Yet the voltage is off by about 0.2V.  Oh well. 

Where are you measuring the voltage to compare with the reading, at the sensor or power supply output?

A lot of factors can affect the variation, wire resistance, noise and ADS unit itself.

The gain should be 256mv but can vary down slightly.

I found that each ADS1115s requires slight adjustments.

Small capacitor, 1uF or 0.1uF at the resistor divider input voltage also help.

0.2v is only 1.5% error.

[mlord]

Found it.  I was not using the characteristics of the ADS1115 correctly in the calculations.

 

The ADS1115 ADC returns absolute (corrected) voltage measurements.  So to get the voltage at the ADS1115 pin, the calculation is simpler than I was doing.

 

Just this:  v = 4.096 * pinval / 0x7fff;

Then apply scaling per the two resistors of the voltage divider.

 

I was mistakenly "correcting" it against the measured 3.3V from ADC0 of the ADS1115, which is the Right Thing^tm to do for the thermistors, but not for anything not referenced from the ESP32 "3.3V" supply.

 

Fixed.

 

EDIT: And now that the calculation has been corrected, I've opened up my main (real) Dew Controller, and found the issue there as well:  The GND leg of the resistor network was not soldered correctly -- just floating, which explains how applying 12V there caused the ADS1115 to misbehave on all inputs.  FIXED.

 

Now seeing 12.374378 as the voltage reading, which is probably more accurate than my multi-meter which shows 12.38V. 

 

Using a 1/4 voltage divider is only safe for voltage input up to about 14.4V though, and I would like more margin there for car batteries and the like.  So the wiring / code will be updated to use a 1/5 voltage divider instead, giving sufficient margin to protect things.

 

Cheers

Edited by mlord, 13 July 2024 - 02:10 PM.

[mlord]

Here is the newly updated wiring diagram for this project.  I have rearranged the drawing around the resistors for the voltage measurement (top centre), and changed the ratio to 4:1 (40K:10K) (which actually gives a divide-by-five on the voltage for the benefit of the ADS1115 module).

 

The diagram here, shows the full wiring for a Smart 2X Dew Controller.  If only a single channel (1X) is needed, then omit the DewHeater-1 connections, the corresponding LR7843 Module, and Thermistor-1 with its 10K-ohm resistor.

 

[Click on the image to view a larger, higher-quality version]

 

For the OPTIONAL voltage measurement section, one can use any combination of resistors desired, in the 5K to 50K range, so long as the ratio between them remains 4:1.

 

It may be easiest to simply use more of the same 10K resistors already required for the thermistors.  In this case, wire four of them in series to obtain the "40K" value, plus one more for the 10K value.  That's what I did myself, using high-quality ones rated for 0.1% tolerance, meaning they result in very accurate voltage/temperature readings!    Any wattage rating will do for all of the resistors, as they don't carry any significant current.

 

Digikey and Mouser are good sources for resistors of any tolerance, including 0.1% ones.  Eg. https://www.digikey....R1002B/21679704

 

Firmware support for measuring/reporting the voltage is now available in HBG3 firmware v8.51: https://www.cloudyni...0#entry13564324.  CPWI and the Celestron hand-controllers can show the current voltage reading.  The use for this, is to know when the battery is becoming overly depleted.

 

When acquiring an ADS1115 module, note there are two commonly available module styles.  Both have exactly the same "stuff" on them though, so which you choose doesn't matter electrically.  I chose the skinny style shown above, because I found it easier to tuck into my enclosure with everything else.  All ADS1115 chips have a built-in Programmable Gain Amplifier (PGA), so don't worry about adverts that mention it or that fail to mention it: they all have it.

 

As always, building this design around the HomeBrew Gen3 (HBG3) means one also gets Nunchuck slew/focus capability, and "free" WiFi, Bluetooth, and USB connectivity for a connected Celestron mount.  The design can also be used standalone, with no AUX connection to a mount, by adding a connection from the 12-16V Dew Power Input, through a diode, to the labelled 12V pad of the HBG3 (just below the GPS pads).  In this fashion, it can be used with any brand of mount, and yet will still work with CPWI for Dew Control over any of the connection methods.

Edited by mlord, 14 July 2024 - 10:13 AM.

[scopewizard]

Mark,

 

It is recommended that input be max VDD+0.3. This mean 3.6v. With a divider 5, max 18v is more than needed. 

A car battery (lead)  rarely gets above 13.6, lithium, on the other hand, can be as high as 14.8v.

I use a LiFePO4 deep cycle 100ah which peaks at 14.2v when charging but after 10 mins disconnected, settles at 13.85v.

On the other hand, my 65ah, peaks at 14.6v and settles at 14.4v.

The sad part is my ASI2600 cooler is limited to 14v so the 65ah is only used for the laptop.

[mlord]

It is recommended that input be max VDD+0.3. This mean 3.6v. With a divider 5, max 18v is more than needed.

That's based on the Absolute Maximum Ratings.  I use the preferred operating range instead, where one limits the max voltage to no more than Vdd (3.3V here) on any input.  4 * 3.3V = 13.2V, not good enough.  Thus the 4:1 divide-by-5 ratio instead, for max input of 16.5V.

 

This allows for voltage drops on Vdd with an overall safety margin.  In my own Dew Controller, there is a voltage drop on Vdd under load, with it measuring as low as 3.25V instead of 3.3V.

 

Cheers

Edited by mlord, 13 July 2024 - 12:49 PM.

[scopewizard]

That's based on the Absolute Maximum Ratings.  I use the preferred operating range instead, where one limits the max voltage to no more than Vdd (3.3V here) on any input.  4 * 3.3V = 13.2V, not good enough.  Thus the 4:1 divide-by-5 ratio instead, for max input of 16.5V.

That is exactly what I do.
 

[mlord]

I have again updated the wiring diagram above, to make it easier to follow, and now showing the 3.3V/GND connections going to the I2C pads of the HBG3 where they are easiest to connect.

Edited by mlord, 14 July 2024 - 08:17 AM.