Yeah maybe 50+k is better than 1.8k for I2C, that's above my pay grade.
I've seen others complain about them being so low as well so still thinking they are 1.8k but can't be certain now, thanks. I searched that page you linked which is official and no mention of 1.8k or any other values.
I'm not trying to bring you down but It looks like you're working on a fairly large project, if you're planning to run 18 I2C devices you might need to rethink things. A few years ago I wanted my controller to expand to large levels and went down the road you are heading on and for me it didn't end well. I attempted to make it work for months, even went to the expense of getting lots of PCB's made. I tried a few buffers, the pca9507 was the best. Running multiple pca9507 like you are I was able to successfully run 22-24 devices with about 100 feet USB cable total but it wasn't reliable. Even with only a few devices connected it wasn't perfect. I hate to say it and I hated to read it when I was doing this, it's just not possible if you need reliability. For any chance of it working you would have to code a strong CRC check and figure out how to handle the bus locking up.
Hi Rob,I'm not trying to bring you down but It looks like you're working on a fairly large project, if you're planning to run 18 I2C devices you might need to rethink things. A few years ago I wanted my controller to expand to large levels and went down the road you are heading on and for me it didn't end well. I attempted to make it work for months, even went to the expense of getting lots of PCB's made. I tried a few buffers, the pca9507 was the best. Running multiple pca9507 like you are I was able to successfully run 22-24 devices with about 100 feet USB cable total but it wasn't reliable. Even with only a few devices connected it wasn't perfect. I hate to say it and I hated to read it when I was doing this, it's just not possible if you need reliability. For any chance of it working you would have to code a strong CRC check and figure out how to handle the bus locking up.
Bottom line is you need to look at other protocols such as RS-485 or CAN bus. If you really want to keep going look at the PCA9615 to split the I2C signals into differential signals, personally I haven't used this as I finally came to accept this isn't the route a person should be taking but this does sound like the best bet.
Here's a good article explaining how differential signals works.
An Introduction To Differential I²C
A few weeks back, we talked about the no-nos of running I²C over long wires. For prototyping? Yes! But for a bulletproof production environment, this practice just won’t make the cut. This mo…hackaday.com
Here's a pic with most of the stuff connected, I had 8 AC power bars connected as well at one point. All that and more went in the trash.
yes, at that scale go plc/scada for industrial setup, or home lab type setup with x96 and cat5/6.I'm not trying to bring you down but It looks like you're working on a fairly large project, if you're planning to run 18 I2C devices you might need to rethink things. A few years ago I wanted my controller to expand to large levels and went down the road you are heading on and for me it didn't end well. I attempted to make it work for months, even went to the expense of getting lots of PCB's made. I tried a few buffers, the pca9507 was the best. Running multiple pca9507 like you are I was able to successfully run 22-24 devices with about 100 feet USB cable total but it wasn't reliable. Even with only a few devices connected it wasn't perfect. I hate to say it and I hated to read it when I was doing this, it's just not possible if you need reliability. For any chance of it working you would have to code a strong CRC check and figure out how to handle the bus locking up.
Bottom line is you need to look at other protocols such as RS-485 or CAN bus. If you really want to keep going look at the PCA9615 to split the I2C signals into differential signals, personally I haven't used this as I finally came to accept this isn't the route a person should be taking but this does sound like the best bet.
Here's a good article explaining how differential signals works.
An Introduction To Differential I²C
A few weeks back, we talked about the no-nos of running I²C over long wires. For prototyping? Yes! But for a bulletproof production environment, this practice just won’t make the cut. This mo…
Here's a pic with most of the stuff connected, I had 8 AC power bars connected as well at one point. All that and more went in the trash.
. I think they look super contrasting , the palette with zoa colors pop . . The entire thing is built with 3/4” walnut vineered plywood , with domino as joinery.
Thanks for the kind words, working on bringing back that GUI.
For the DHT22 you can run a python script like this, if you edit it so only the humidity is saved to the file you can import it in reef-pi using the file driver. If you can get away from I2C its best, I know it's tempting though with 2 wires vs 16.
pimylifeup.com
Thank you Rob, I'll give it a tryThanks for the kind words, working on bringing back that GUI.
How to Set Up a Humidity Sensor on the Raspberry Pi
Great for monitoring both temperature and humidity.
Well, judging from the Atlas Instrument datasheet, which gives some Information on working principle and calibration, I would hazard the guess that it’s similar to pH, e.g. that the „mid-value“ is supposed to be 0mV, corresponding to the ORP value of silver chloride. That probably needs to have a value of zero, but I’m not completely sure about that.Another question, How do I calibrate a single point calibration probe such as ORP?
If I set 225mV for both mid value and second point I always have 225 reading... I'm missing something
Exactly, a high resolution volt meter. The other day someone told me after running it along side his other good meter it's bang on. Heard this many times now.Actually: I wouldn’t at all be surprised if you could in principle connect an ORP probe to @robsworld78 ‘s pH circuit and measure it that way. The circuit does after all only seem to measure an isolated voltage between -700 and +700mV
I've never tested it for ORP but a while ago someone told me to add an extra resistor and it would work with ORP so I've actually revised the board since you got yours, it's even smaller now. Currently it has a solder jumper to activate the extra resistor for ORP. I haven't really tested it yet but I bought a cheap ORP probe and some 225mV calibration solution. I don't really know how to test it properly so I'm just going to see how close it is to 225mV, figures crossed. Nice, can you elaborate on why you need that extra resistor ? Change the amplification on the OP-Amps ?Exactly, a high resolution volt meter. The other day someone told me after running it along side his other good meter it's bang on. Heard this many times now.
Well, you basically measure the voltage between the probe‘s contacts. Since this voltage can also be negative you have to bias this voltage to a point between VCC and GND. This bias point should be identical for pH and ORP, but might be different if you are only interested in specific value ranges.Let's see if you can tell me?
www.reef2reef.com
Exactly how I would have said it.
I had a feeling it was due to the negative voltage, couldn't remember exactly though but knew you would know and you did. 
Awesome as usual I went to Tropic Marin all for reef and that way all I have to dose is one thing....works really well but man your tanks always look so much better than mine, lol...if you want to ship any of those SPS frags I will gladdly pay for shippingOne of my tank. Now the sps are growing at a rate and has passed a size that I can sustainably frag a few (green slimer, forest fire digitata , red milli pora, strawberry shortcake ) for testing in pico tank
Here is a close up of the green slimer colony . I have to frag it, otherwise it will shade the other acro frags glued beneath
strawberry shortcake colony
Pink stylo
I really want to test a minimal reef-pi setup that can keep at least some of these across. I am able to keep green slimer and monti right now. Without any dosing . But over the last few months I have sourced pretty awesome 12v brushless motor that generates ample flow, and now that dosing systems are tested with all for reef based alk/ca supplement , I think i have all the things needed. I am really excited about this. It will be so cool to have a pico tank with a sizable sps colony as the center piece , all grown out with reef-pi in a very affordable and open setup. That will be an awesome milestone
Hmm, can‘t quite elaborate on the hysteresis with certainty, but I think it should work like your first thought, e.g. shut down on target and turn on below target-hysteresis.
