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  #101  
Old 09-07-2019, 01:53 AM
Corpze (Daniel)
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Hi again.
I recieved two new boards (4ch irf540) but both of them puts out 12v regardless if the respective channel is activated by the arduino or not (the led on the 4ch mosfet board is only shining when the arduino output is activated by the code ( as it should be)

But even if the output from the arduino is 0% and the LED on the mosfet board is dark, it is 12v to the heater band and it gets really hot.

My connections is correct on the low-level side, as the LED is on or off when the arduino activates the output.

The 12v side is connected as 12v+ in and ground (shared ground with the arduino)

The outputs are connected 12v+ and ground from each channel to a RCA connector with same ground as the casing (and arduino)

I just can't seem to understand why the mosfet is always on?
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  #102  
Old 16-04-2023, 11:05 AM
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ChrisV (Chris)
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After a long break I've made many modifications to the dew heater. Its now a simple stand alone unit but can also be controlled via USB on a PC to monitor it and change mode/settings. The basic Arduino coding and .exe are here

https://drive.google.com/drive/folde...gR?usp=sharing

Might take a few days to re-write all the instructions
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  #103  
Old 13-06-2024, 08:00 PM
inertia8 (Australia)
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Just wanted to say, excellent work!

Shall be building one of these after deciding upon which screen to use.
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  #104  
Old 14-06-2024, 04:02 PM
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ChrisV (Chris)
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Inertia8

I don't use a screen anymore. Makes construction simpler and frankly it was just one extra thing that could go bung. I made a PC app that sets it all up. You can then just let the box run and do its own thing; one less thing to think about while imaging. Or you can have it connected to a PC to see what's going on, or change settings. I also redid the feedback controller; uses PID and is much better. This is also good cause it greatly reduces power consumption!

Instructions should all be on the Google drive link with my last post. But I will go through and check, and add some photos of new build. But any questions reply in the thread or PM me.
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  #105  
Old 14-06-2024, 08:05 PM
inertia8 (Australia)
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Cheers Chris.

Mines actually for a 10in dob and visual observing.
I had severe dew last weekend and had my observing cut short. Telrad and finder dew up, then secondary. Primary looked horrible but it does under red torch...

At a minimum I'm doing it for telrad, ep and eyepiece. Figured I would do the secondary but that looks tricky with the thin foil on one spider for wiring.

I would prefer a screen just to confirm what's going on etc. can the little oled be dimmed right down?
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  #106  
Old 15-06-2024, 07:33 PM
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The OLED. I just put some red translucent plastic sheet over it. Dimmed it and kept the dew out!!
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  #107  
Old 18-06-2024, 09:05 PM
inertia8 (Australia)
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Excellent, I've done a bunch of ordering from Ali.. along with the kit to try and repair a fried Goto board or two..
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  #108  
Old 09-01-2025, 11:53 PM
pinakoza
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Thanks, Chris, for sharing all these precious information
I have checked other similar dew heaters as well, but yours is the simplest with no need for any custom PCB, few ready to buy components, easy to build, and still with great functionalities. I already ordered some components that I was missing in my stash - like expansion boards, Mosfets, AM2320 etc.

For dew heater, I mainly use the element from inside the Pipe Heating Cables available here in Canada. I cut the desired length and connect it with either an old USB cable (for 5v), or some 18-20 AWG wires for 12v application. I have been successfully using them since 3-4 years now with ZERO issues. They are all covered by a Velcro tape (on one side) and a thin cotton tape over the Velcro, while the element is lightly covered by the same thin cotton tape.

This time, I want to go for Planet photography using my 8" and 12" Newtonians, and I want to have a smart control on dew heaters so as not to overheat the primary mirror. That's where I came across your smart dew heater page.

I will keep you posted with the progress. I am attaching some pics of my dew heaters.
https://photos.app.goo.gl/mgBL2ZYQBx3RDiWc7
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  #109  
Old 25-01-2025, 12:07 AM
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Finally Working

Hi Chris, thanks for your support.

I finally made one using the Dew Heater v.6.2.3. Most hardware is connected and working as intended. I tested it on PC and Button mode; both of these modes working great.

The sensors that I have used are AM2320 and DS18B20 with 16x2 LCD and 4ch Mosfet board. I haven't connected any heater output jacks yet, but just tested the whole thing completely using ice packs (to cool down DS18b20) at room temperature.

PC app is truly great. I love it. It displays lot of useful information. Thank you very much for making this app

How I made it finally work after 3 days of disappointment?
By adding 2 sec. delay. I figured it out by random testing only:
------------------------------------------
sensorAmbient.ino file
------------------------------------------

// get ambient temp & humidity data from AM2320 or BME280 sensor

#ifdef AM2320_ON
void resetAmbientSensor() {
am2320.begin();
}

void getAmbientData() {
// read ambient temp and humidity - takes 100s of msec?.
humidityAmbient = am2320.readHumidity();
delay(2000);//EXTREMELY IMPORTANT DELAY
temperatureAmbient = am2320.readTemperature();
calcDewPoint();

----------------------------------------
This one line changed everything - from disappointment to joy
I hope this will help someone having similar issues of getting readings from AM2320 sensor.

Last edited by pinakoza; 25-01-2025 at 03:08 AM.
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  #110  
Old 26-01-2025, 02:37 PM
pinakoza
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Pictures

Sharing some pictures of my dew heater.
https://photos.app.goo.gl/mgBL2ZYQBx3RDiWc7
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  #111  
Old 28-01-2025, 12:57 PM
Leo.G (Leo)
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This seems like an interesting thread I will go through later. I still have my old camera thingie here, a row of resistors I plugged into 12 volts which got just warm enough to keep my camera lens clear but not warm enough to interfere with the mechanical (greased) components of the Nikon lens.


Sorry Chris I haven't been through the thread yet but did you make your own dew straps too or are you buying the cheaper camera type ones?
I know the camera ones come in a variety of sizes which will fit around certain sized scopes and good prices.



Quote:
The OLED. I just put some red translucent plastic sheet over it. Dimmed it and kept the dew out!!
I keep various shades of nail polish here mainly for locking screws and components on electronic circuits but also occasionally for dimming nuisance LEDs on boards.
Nothing expensive, clearance price stuff from the reject shop. Also great for marking locks and keys when you're too stupid to figure out big locks generally take big keys (me)....
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  #112  
Old 29-01-2025, 09:04 AM
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Leo

Thanks for your comments. In the past I have made my dew straps. I haven't tried the resistor method but I'm sure its great. I have used nichrome wire covered in heatshrink (I have some instructions somewhere to sort out length needed ...). I lay this on aluminium tape which will be on the scope side, put gaffa tape on the back then insulation tape to keep the heat in & hold it all together, and add some velcro straps.

I haven't used ready made heater straps but just got some cheap ones on aliexpress to try out. As is, they can only support the auto-ambient mode of heating (uses dewpoint v ambient temp to drive it). But I would have to replace the cabling (or just add another cable) as I use 4-core cable for the auto-heater mode which requires a temp sensor on the scope.

Nail polish - good idea. Also be good to keep moisture out of the unit.
I'm currently revising the instructions and some of the coding as its all a bit of a mess; but WORKS (well except for some current issues with AM2320)

Last edited by ChrisV; 02-02-2025 at 04:13 PM.
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  #113  
Old 31-01-2025, 12:00 PM
Leo.G (Leo)
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Thanks Chris!


I have Nichrome wire here I bought to make some straps but until I just read this I forgot I even had it. The only reason I didn't progress with them was I didn't want to use duct tape, it peels away and leaves so much stickiness. I'll find something else which is simple or get the old sewing machine out and make something decent



A little trick with Nichrome wire, since it can not be soldered, there are little crimp fittings used for fishing, they are great for crimping a connection wire to Nichrome wire and very cheap.
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