reef-pi :: An opensource reef tank controller based on Raspberry Pi.

[Schreiber]

In a semi-related question for any electronics experts; I have an opportunity to pick up some Tektronix 2215A oscilloscopes. Being that I know very little about oscilloscopes, I'm hoping to get some input or advice. I can get them for about $20 each. I did pose this question to an electronics expert who is an active member of this forum, in a PM, but I believe he is on vacation and if I am going to buy the oscilloscope(s) it has to be by tomorrow afternoon.

Any input would be appreciated!

They're great for verifying PWM output from the PCA9685.

 

[crusso1993]

They are $ 300 + on E-bay

That's 100% worth it. If for nothing else, just to play around with.

if they are functional pick them up for sure. I would check for screen burn if they have been used a ton other than that they should be pretty bulletproof

They're great for verifying PWM output from the PCA9685.

Thank you all for the input! It is much appreciated!

 

[Alaa]

Hi
Help needed, i need to connect second PCA9685 to my pi setup using goby hat from @Michael Lane (needed to control 10 channel lights and additional 2 fans) my understanding is that the VCC on PCA9685 should be connected to 3.3V, so i figured that i can use the connector attached and connect the second PCA9685 (will be located in a separate box from R-Pi) using 3.3V, SDA, SCl, and ground then give it a proper address.
the pH connectors on the goby Hat has 5V so i can't just use it for my second PCA9685.
Will this work or the PCA need to be chained one to another for them to work, also can it damage my Pi (already fried one).
My second option (i really don't like it) is to use another r-pi with a reef-pi build for lights only.

Thanks

 

[Ranjib]

Hi
Help needed, i need to connect second PCA9685 to my pi setup using goby hat from @Michael Lane (needed to control 10 channel lights and additional 2 fans) my understanding is that the VCC on PCA9685 should be connected to 3.3V, so i figured that i can use the connector attached and connect the second PCA9685 (will be located in a separate box from R-Pi) using 3.3V, SDA, SCl, and ground then give it a proper address.
the pH connectors on the goby Hat has 5V so i can't just use it for my second PCA9685.
Will this work or the PCA need to be chained one to another for them to work, also can it damage my Pi (already fried one).
My second option (i really don't like it) is to use another r-pi with a reef-pi build for lights only.

Thanks

How you are powering pi? If possible get 5v output from the source and use a 5v to 3.3v converter (there are plenty cheap ones in amazon) to power the second pca9685. You can also power it from pi’s 3.3 v , but be aware of current draw. Everything collectively should stay below 500ma and any single pin should not draw more than 80ma. Pi when powered feom gpio can only supply 1a . When powered by micro usb connector , pi can supply more than 2a (assuming 2.1a supply and 100ma draw from pi zero). It’s a good idea to throw 100 and .1uf capacitors in between sources. I always keep separate pi as plan b. In case things go south. I had worst power induced issues with pwm and light controllers :-/

 

[Alaa]

How you are powering pi? If possible get 5v output from the source and use a 5v to 3.3v converter (there are plenty cheap ones in amazon) to power the second pca9685. You can also power it from pi’s 3.3 v , but be aware of current draw. Everything collectively should stay below 500ma and any single pin should not draw more than 80ma. Pi when powered feom gpio can only supply 1a . When powered by micro usb connector , pi can supply more than 2a (assuming 2.1a supply and 100ma draw from pi zero). It’s a good idea to throw 100 and .1uf capacitors in between sources. I always keep separate pi as plan b. In case things go south. I had worst power induced issues with pwm and light controllers :-/

Thanks for your response
I'm using the original pi power supply through the micro USB, as i understand the PCA V+ pin is not used to power the chip (PCA pinouts) it is used for the servo, before in my original setup (not using goby hat) i didn't connect the v+ at all and was able to control the lights, however in the (PCA chaining) tutorial they used a separate power supply that is where i get confused.
to rephrase my questions,
1- Can i add a second PCA through my connector and not being chained through the Goby Hat PCA?
2- Do i need a separate power supply 5V to the second PCA?

 

[BenB]

Hi
Help needed, i need to connect second PCA9685 to my pi setup using goby hat from @Michael Lane (needed to control 10 channel lights and additional 2 fans) my understanding is that the VCC on PCA9685 should be connected to 3.3V, so i figured that i can use the connector attached and connect the second PCA9685 (will be located in a separate box from R-Pi) using 3.3V, SDA, SCl, and ground then give it a proper address.
the pH connectors on the goby Hat has 5V so i can't just use it for my second PCA9685.
Will this work or the PCA need to be chained one to another for them to work, also can it damage my Pi (already fried one).
My second option (i really don't like it) is to use another r-pi with a reef-pi build for lights only.

Thanks

The PCA9685 operates with a supply voltage range of 2.3 V to 5.5 V and the inputs and outputs are 5.5 V tolerant.

And you can connect more than one like this:

And give it a proper address. https://learn.adafruit.com/16-channel-pwm-servo-driver/chaining-drivers

If the second pca9685 is in another box that is further away than 1 meter best is to use a shielded cable.

 

[Alaa]

The PCA9685 operates with a supply voltage range of 2.3 V to 5.5 V and the inputs and outputs are 5.5 V tolerant.

And you can connect more than one like this:

And give it a proper address. https://learn.adafruit.com/16-channel-pwm-servo-driver/chaining-drivers

If the second pca9685 is in another box that is further away than 1 meter best is to use a shielded cable.

thanks
the point is that i cant chain them like that because of the goby hat, so i guess ill try to hook it up through the pi connector and see how it goes

 

[Michael Lane]

@Alaa The goby board exposes 12 pwm outputs at 3.3v over Light1, Light2, Light3, and Doser ports.

Pca9685 can work with 5v, so you may not need to convert anything unless your target requires it. You could possibly just connect to ph2.

It sounds like you have a lot going on with this build. Do you have a build thread that shows more details? I'd be happy to take a look and help where I can.

 

[redwayjay]

Recommendations for the following probes to use with Reef PI;
PH
Salinity
ORP

 

[AbjectMaelstroM]

Recommendations for the following probes to use with Reef PI;
PH
Salinity
ORP

Not exactly sure if that's a question or a statement... But if it's a question regarding recommendations for probes to be used with ReefPi then:

pH: double junction with BNC connector like an Atlas scientific, Milwaukee, or one sold by BRS. I've got the Milwaukee one from amazon, $40.

As for ORP/Salinity, to my knowledge ReefPi does not support them at this time. @Ranjib will be better suited to answer that.

 

[Des Westcott]

Recommendations for the following probes to use with Reef PI;
PH
Salinity
ORP

I asked about Salinity recently. Let me see if I can find the post

 

[Des Westcott]

Due to their high cost, frequent need of calibration and less usefulness (compared to other sensors) I have not tinkered with ec and orp probe.
That being said, I think the ezo ph driver will work as it is for orp and ec as far as reading goes. Calibration and rest needs to be done out of reef-pi using atlas scientific libraries

There you go.

 

[Cali9dub]

Wonder if any of you gurus could take a new vertex cerebra VII and get it functioning? They are out of business and never finished the raspberry pi based controller. It has a brain, touchscreen and controllable powerbar. I know a guy who got stuck with quite a few and might let someone get one to see what they can do. Just curious ....

 

[Alaa]

Hi
@Ranjib, @Michael Lane, @BenB
Thanks for all your help, i connected a second PCA9685 as suggested earlier and it is working fine, i was not brave to use 5V from the goby hat since it is the max PCA can handle so i thought it is best to use 3.3V as standard.

 

[Ranjib]

Wonder if any of you gurus could take a new vertex cerebra VII and get it functioning? They are out of business and never finished the raspberry pi based controller. It has a brain, touchscreen and controllable powerbar. I know a guy who got stuck with quite a few and might let someone get one to see what they can do. Just curious ....

We can tinker with it and salvage what's usable. It will be really cool if we can get reef-pi running in one of those. I dont know how many custom components it has, and how easy it will be to get those working with reef-pi. If its a lot of work, its probably not worth , since theres only a handful of these units present. But without testing out, its hard to say how much effort involved

 

[Ranjib]

Hi
@Ranjib, @Michael Lane, @BenB
Thanks for all your help, i connected a second PCA9685 as suggested earlier and it is working fine, i was not brave to use 5V from the goby hat since it is the max PCA can handle so i thought it is best to use 3.3V as standard.

woot , keep us posted

 

[Des Westcott]

HELP!!

Got up this morning and the reef-pi is dead. Nothing running. NOt sure when this happened. Was fine last night at around 23H00 but no Alerts from the 05H30 water change that should have happened this morning.

Rebooted the Pi and got the following from the screen connected to it.

Has the card died?

 

[Ranjib]

HELP!!

Got up this morning and the reef-pi is dead. Nothing running. NOt sure when this happened. Was fine last night at around 23H00 but no Alerts from the 05H30 water change that should have happened this morning.

Rebooted the Pi and got the following from the screen connected to it.

Has the card died?

From the log it looks like Sd card got corrupted

 

[Des Westcott]

From the log it looks like Sd card got corrupted

Thanks Ranjib

That's what I surmised. In the process of setting up a new card.

I really wish I had got round to backing up / making a .img of the old card.

Live and learn I guess.

 

[redwayjay]

There you go.

Thanks, Des. Out of curiosity besides the tinkering factor do you think this will still be viable option to Apex once the Coralife Hydros 4 is released?