I just bought an RS232 controlled Relay. I have looked all over the ncd website and searched the forums and have found a lot of documentation, but not a hardware datasheet.
*What temperature range is the product rated for?
Also, I want to use the this device like a watchdog timer, to reset the power to my computer and cell modem if they stop operating, however, my cell modem has a lot of capacitance, so I need the power off for about 5 seconds. If I use the pulse timer, it only turns off the relay for a very brief moment.
How can I achieve this?
Here is the product description of what I bought:
Relay Controller 2-Channel General Purpose SPDT + 8 Channel ADC ProXR Lite - 5 Amp SPDT
RS-232 Serial Communications Module with MAX3232 ZRS - ZRS-B, DB-9 Connector
So what I would recommend doing for what you described is to use the simple duration timer command. You can issue a duration timer command to turn the relay on for say 10 seconds. Every 5 seconds or so send the command again, this will reset the timer to 10 seconds and the relay will continue to stay on indefinitely as long as you keep sending that command. If for some reason the board does not receive the command then it will turn the relay off. The relay will then stay off until it receives the command again.
Now if that does not work for your application then the alternative would be to use the Watchdog pulse timer as you described. Connect the relay output on our board to a simple timer relay like this.
A short pulse from the relay on our board can trigger that relay to turn on for whatever duration you set it to.
If you have any other questions on this please let us know.
Thank you for your reply.
-I’m glad to hear the temperature range.
-The duration timer won’t work for me, because once my computer turns off, I won’t be able to send serial commands to turn it back on.
-I’m disappointed that I need to buy another piece of equipment to implement the reset feature I need.
-If there is any other way, let me know. Otherwise, thank you for your time.
Yes. I do have programming experience. Our computer runs Debian linux. I wrote a python script to send it a serial command every 2 seconds to implement the “tick” on the watchdog. And I program our main product which uses a PIC18F46k20, which isn’t too different from the 18F14k22 you have on your PCB.
Unfortunately, our computer only has 3 USB ports on it and we are using all of them for other things. That is why I am using the serial connection. But, let me know what the USB solution is. If we had to, we could try moving one of the USB devices to serial.
The minimum pulse time is 10 seconds. I would like it to be between 10 and 15 seconds. It shouldn’t be more than 60 seconds.
Ok, so being a programmer myself the first solution I would suggest is this board with the optional Particle Photon IOT interface module:
The Particle Photon module is a programmable ARM based device. It has built in WiFi and USB. Of course you can turn WiFi off and just use the USB interface. You can write a really simple script in C/C++ that will accept commands and execute them. The application you have detailed would take me around 1 hour to write the code for in this board using the libraries we already have available. Also if you’re a programmer and are proficient with C/C++ you’re going to love developing with the Photon, it’s a dream and I’ll never go back to Pic based products ;). I know it’s a little more expensive but it has WiFi and USB built in, Particle also has a cloud solution you can use if needed so the value you get out of those 3 things along with being extremely easy to develop on it’s more than worth the extra money.
Now if you just absolutely have to have RS 232 interface that is still possible with this board. You can add a DB9 serial interface module to it. To do that you will need the two following devices:
The XBO module(first board) plugs in over the top of the Photon, then the ZRS module(second board) plugs into that giving you and RS 232 connection to the Photon module.
With this hardware setup you can do pretty much anything you could possibly need to do with 2 relays over a USB or Serial interface, and easy to.
If you have any questions on this please let me know.