Sainsmart raspberry pi

Sainsmart raspberry pi DEFAULT
Hi.

You relay board will no doubt be active low, that means applying a low signal to the IN pin turns the relay on and applying a high signal turns it off.

But now comes the problem , most of these boards use 5v for the control circuit, so 5v is applied to the control circuit and a low signal applied to the IN pin allows current to flow turning the relay on,
but when you want to turn it off you have to stop that current flow, but because the pi gpio is only v it will allow some current to flow sand so keep the relay on.

viewtopic.php?f=91&t=&start=25

The best way to solve this problem is to use two ULNA chips as an interface between the pi gpio and the relay board this will also make you relay board behave as active high which is what you were trying to do with your inverter circuit.

your linked web page also says the relay board is 12v so you will need to connect a separate 12VDC power supply to the relay board.

Typical wiring diagram for 2 ULNA and 16 with relay board with active low
Image

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16 Channel Sainsmart relay board connected to raspberry pi zero w, hydrosys4 app not stopping relay / turning off relay

Within the Hydrosys4 app Settings page in the actuators test section I can set the app to pulse the GPIO and I get the LED indicator on the relay board and the relay engagement but the relay does not disengage after the specified on period.

I have verified via the command line that I can turn on and off the relay board using the wiringpi GPIO interface library commands. The command turns off the relay and the command turns on the relay.

Below shows the current wiring setup between the Pi and the 16 channel relay board. Power is coming from a Ma 12vdc adapter to the relay board and then supplying 5vdc to the Pi. Wiring Diagram

The below shows the HardwareSetting page within the hydrosys4 app and the arrows point to the line where I have set GPIO 4 to trigger as the water2 output type. Hydrosys4 HardwareSetting page

The below screenshot shows the actuators test page where I can trigger the assigned water2 output for 10 seconds but the relay does not disengage after 10 seconds. Hydrosys4 Settings page

To reiterate my question: I can trigger via command line the relay to turn on and off but within the Hydrosys4 App I can get the relay to turn on but not off. I'm asking if anyone has any experience with Hydrosys4 and this issue of the relay NOT turning off? How did you fix this issue?

asked Jun 14 at

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User avatar
bitbank
Posts:
Joined: Sat Nov 07, am
Location: Sarasota, Florida

Re: Sainsmart " TFT on RPi3 without shield

Tue May 30, pm

I got a refurb of the same board for 1/2 price. There isn't enough details on the Amazon page to tell you that it only works with a bit parallel interface (not SPI). I did an experiment yesterday trying to connect it in a bit hacked bit-bang arrangement, but couldn't get it to work (I have successfully written my own code to talk to other SPI LCD displays such as the ", " and ").

The way I've seen people make it work with the RPi is to use a few shift registers to turn the RPi's SPI into parallel signals. There is an Arduino 'shield' to do this, but by the time you buy it, you've spent too much on this under-performing display.

Advice - cut and run.

There is a " x LCD from Waveshare (or equivalent) that has a 4-wire interface. This would be easier to connect to the RPi.
The fastest code is none at all :)

User avatar
marciokoko
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Joined: Sat Aug 27, pm

Re: Sainsmart " TFT on RPi3 without shield

Tue May 30, pm

Thanks. I do have a couple of shields that came with the screen, not sure if those would make a difference:
One more thing, Ive already followed part of that tutorial and I thought it would be a problem but I followed it anyway because it never mentioned something so obvious. I changed enabled the spi interface and went ahead and changed the fb0 (hdmi) to fb1(spi). So now after downloading the drivers but rebooting, the screen stays at the color kaleidoscope or whatever screen.

Is there a way to boot-hdmi with a key combination or something?
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User avatar
bitbank
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Joined: Sat Nov 07, am
Location: Sarasota, Florida

Re: Sainsmart " TFT on RPi3 without shield

Wed May 31, am

The shield for the Atmega is the one which will convert SPI into the parallel signals needed for the LCD.

You should be able to edit the /boot/config.txt on another computer to get you back to your original (working) settings.
The fastest code is none at all :)

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