$300 Food Computer - MVP


Yes. You can make changes there, then run the Cron.sh script to load it; this is easier than editing cron directly from the command line).


So I edited my light schedule in the MVP_cron.txt file to have the lights start withing the next thirty minutes so I could witness them turn on, but they did not go on. I kept playing with the times just in case I had the wiring in the relay set to the off on startup position even though I was pretty sure I had it correct. I rebooted the pi every time I made changes to the schedule. Eventually I was tired of playing with the txt file and set the time to what I ultimately wanted it to be, 5 am to 11 pm, and went to bed. Sure enough the light came on at 5 am. Is there some kind of lead up time or does a set light schedule only work the next day? Everything seems to be running smoothly now.


Editing MVP_cron.txt, by itself, doesn’t do anything. The file has to be transferred over into the system application cron by running /home/pi/MVP/python/Cron.py; this application actually changes cron. There should be no need to reboot, and the changes should take effect immediately.
Sorry for the confusion.


The time stamp on my humidity measurements appears to be 4 hours in the future. The temperature measurement time stamps are correct. Is there a way to correct this? I have the correct time zone on the pi.


The timestamp is set to Greenwich time (for consistency across MVPs), rather than local time. Not sure how the temperature is local time


Has anyone had any luck using there phone to view the data on the mvp? I do not have a static ip at home?


It can be done, but takes a bit of work. I have several MVPs set up to do this.
You have to set up a ddns (dynamic DNS) service to handle the ip issue; many routers have this built in to their software. Then you have to do a port forwarding to make the server port accessible from outside your network. It is best to also reserve the internal ip address of your MVP so your router does not re-assign it at some time in the future. There are more details here:


Is there a way to export or at least copy the temp and humidity data to a spreadsheet?


You can export data, but it is a bit of work. Take a look at these two tools:


The link for the rasperry Pi 3b and the canakit power supply on the BOM no longer link to an active product on Amazon. Now it appears the 3b+ is the available option. Are there any changes needed when switching the mvp setup to a 3b+ Pi? Thanks.

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None. The 3B+ is a better computer for the same price. It is a bit faster, more memory and has wi-fi built in. I have used them both, but now prefer the B+.


Thanks! Appreciate it.


Where do I find the temperature set points to adjust them? I found that it’s variable.py I’m looking for but can’t find it.


Look in home/pi/MVP/python/env.py
It is a part of the JSON structure. You can edit it with a text editor as well as the Python IDE.


Thank you Webbhm. The best option for us for really cheap monitors is Goodwill for $5. But they are dvi or vga input. Do the raspberry pi’s work fine with hdmi to dvi adapters/adapter cables? I appreciate all your help. We are building more to put in another school.

Example adapter cable I’m looking at for our projects:

HDMI to DVI, Benfei HDMI to DVI Cable Bi Directional DVI-D 24+1 Male to HDMI Male High Speed Adapter Cable Support 1080P Full HD Compatible for Raspberry Pi, Roku, Xbox One, PS4 PS3, Graphics Card https://www.amazon.com/dp/B07D6RL3VN/ref=cm_sw_r_cp_api_i_gcoRCbWX0CJA4

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Afraid I know nothing about HDMI/VGA converters. Since the Raspberry is standard HDMI, I would think it should work. At that price, go for it; and let us know now it works.


I don’t seem to have a Cron.py file in my python folder. When I type /home/pi/MVP/python/Cron.py I get back “no such file or directory”. I’m trying to change my lighting schedule using MVP_cron.txt


Sorry, my mistake. It is a shell script, not a Python file.
You want to run /home/pi/MVP/scripts/Cron.sh



First of all many, many thanks for you and the community. You are douing a great job here and inspire a lots of people!

I’m building my first Food Computer in Poland with some parts I can reuse. I already got my old Rasberry Pi 1 and here comes a problem. This version of RPi has only 13 pairs of pins (not 20 pairs like PRi 3. I’ve studied pinouts for both and I think there won’t be any problem connecting Si7021 (3V3, SDA,SDL,and Ground are at the same place) but Ralay connection will probably give me some work to do as there are no Digital I/O numbered GPIO5,6,13 and 19. Could you please give me some instructions where to change my addressing?

PS. Just installed MVP and scripts. Everything works ok. When building scripts I’ve seen that Si7021 is working (tests shown some correct temp and humidy data). After restart I can log into ssh and web data dashboard (no data collected yet, just some old temp data already in database).

May be a long shoot but is it at the beginning of /home/pi/MVP/scripts/Relay.py? is it the only place to change this settings?
# Author: Howard Webb
# Date: 7/25/2017
# Code for managing the relay switch

import RPi.GPIO as GPIO
import time
from LogUtil import get_logger


Relay1 = 29 # Fan
Relay2 = 31
Relay3 = 33 # LED
Relay4 = 35 # Solenoid

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Easy way to better regulate the water level and keep it consistent. Simply fill a water bottle up and put it in one of the holes as shown.