MV1 Batches 1 & 2 (MV1-0001-0074) - Hardware Design & Shipping Updates

The purpose of this thread is to communicate the status of product development for the MARSfarm Version 1 (MV1). When we began this process in the Summer of 2021 our goal was to release the MV1 by the Fall of 2022. To manufacture the MV1 we leased a 3,500 sqft warehouse and secured an SBA loan to purchase machinery and inventory. We are extremely appreciative of all of our customers who have believed in our vision for this product and are committed to exceeding their expectations.

As a company that manufactures products used in schools by students, we are committed to building high-quality products that are safe. To demonstrate this commitment, we have chosen to be transparent with our customers, some of whom have been waiting for months, to receive an MV1.

FAQ

Why was the first production batch (scheduled to ship 11-22/-2/23) of MV1s delayed? - A defect was discovered during testing. Specifically, a resistor on our printed circuit board overheated.

When will my order ship?

  • Orders received before 11/30/2022 - First two weeks of March
  • Orders received after 12/01/2022 and before 04/01/2022 - Last two weeks of April
  • Orders received after 04/01/2022 - July 2023

Please check your MARSfarm Invoice or contact peter@marsfarm.com for a specific date.

Have you fixed this problem for all of the units in production batch 1? - Yes, we identified a resistor as part of the circuit that provides power to the far-red LEDs on our custom LED panel. We modified the MV1 software so that the current will be limited to a point where the resistor in the far-red channel cannot exceed 60C, which is still far below its rated max operating temperature.

Will this impact the performance of the LEDs?- Not significantly. The only spectrum which is being significantly reduced is far-red. Unlike other spectrums of light, which are used for photosynthesis, far-red light has not been proven to increase edible mass. Instead, far-red light is used in greenhouses to simulate shade or dusk conditions, which triggers a process called photomorphogenesis. Because the photons are only used as a signal, only a few (1-3) μmol/m2/s of far-red light are required to manipulate plant morphology.


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Why did this happen? - All four channels of LEDs (white, red, blue, far-red) receive the same voltage (24VDC) from the power supply. Each LED chip drops the “forward voltage” by about 2V when assembled in series. Because there are only four far-red LEDs, the resistors in the far-red circuit were dropping far more power than any of the other resistors.

How will you be testing the first batch of MV1s to verify they are all safe? - The fact that we found this problem before we shipped any units to customers is because of our testing processes. Furthermore, the first batch (25) of MV1s will all undergo a 24-hour “burn-in test”, before receiving their final inspection. That final inspection will include the use of a multimeter to measure the resistance of each resistor to verify it is working properly. Lastly, we will use a FLIR One Pro thermal camera, to verify that no components are exceeding 80C - just to be safe. Which would look like this:

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How will you improve the design in the second batch of MV1s? - We added two more blue LED chips and a red LED chip to the LED panel as well. This way, less voltage will need to be dropped by the resistors in those circuits as well. This will not only decrease the wattage passing through the resistor but will also increase their potential light output.


Yellow highlighted cell indicates Brain PCBA version for Batch 1 (V0.5) and Batch 2 (V0.6)

How does this impact the MV1s capabilities? The red, blue, and far-red LED circuits will now be capable of converting more power into light. To be clear, the current batch of units is more than capable of growing leafy greens and has these max settings for each color spectrum:

PAR for Batch 1 - V0.5 (actual) & Batch 2 - V0.6 (predicted)

umol of photons per meter per second at germination height in the center of MV1

Batch 1 Batch 2
White 286.3 286.3
Blue 14.4 ~40
Red 55.8 ~90
Far-red 2.1 ~8
(all) 363.1 ~430

Total Day Light Integral (DLI) Batch 1

mol of photons per meter per day at germination height in the center of MV1

8 Hours 12 Hours 14 Hours 16 Hours 24 Hours
White 8.2 12.4 14.4 16.4 24.7
Blue and Red 2.1 3.1 3.5 4.0 6.2
(all) 10.5 15.7 18.3 20.9 31.4
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Hello all! As promised, the first MARSfarm Version 1s have been finished!

All of the electrical components go through a 24+ hour burn-in cycle, before passing a thorough final inspection! The very first units began shipping out yesterday, with the rest of the batch to follow over the next week! The parts for the second batch are on the way, and some fabrication on this 2nd batch has already begun. We have appreciated all of your patience while we improved both the safety and functionality of this new technology platform for growing plants. Peter has updated his first post as well, to provide a more detailed timeline of when these batches will be finished.

MARSfarm began as two nerds in a 700 sqft garage/apartment/warehouse on the wrong side of town. We have since moved to a 3,500 sqft commercial facility, and expanded our team! We found a rockstar production manager working for a company that didn’t appreciate her skills, and hired her (Ashley) as a part-time employee. Ashley has allowed us to continue to manufacture other products while I have focused more time on completing the design of MARSfarm Version 1. Ashley will be the first of many (hopefully) full-time employees (send us a resume!) who make and support our products.

It’s been a wild ride for us, but everything we do is focused on creating new products that help you inspire the next generation of farmers and researchers to improve our food system. All this to say: we are proud to show off the first serial number coming off the line!

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Few more photos to share from this week:



FAQ for new MV1 users

1. When does it fill with water?

a. The first batch of MV1s was assigned one of two recipes, by default.
b. To determine which recipe your device is using, simply compare the serial number (located on the top panel) of your device to this list.

  • MV1-0001 through MV1-0013 have the “MV1_Default_Bok_Choy_Spring_2023” recipe assigned by default. This will add 80 ML of water at 9:05 AM daily.
  • MV1-0014 through MV1-0021 have the “MV1_Two_Phase_Bok_Choy_Spring_2023” recipe assigned by default. This recipe will add 80 ML of water at 9:05 AM daily.

c. The amount of water added and the time may vary between recipes. The amount of water to be added is measured in ML. "pump_amount": [ { "start_time": [ 9, 8 ], "setting": 80. Your MV1 knows how to interpret these instructions, in the form of a recipe, and then control the pump to add exactly that amount of water at that time.

2. Should the circulation fan/heater assembly blow the air backward (towards the back wall) or forward when installed correctly?

a. The MV1 heater/circulation fan assembly is designed to push air toward the door. You should not be able to see the fan when looking at the heater through the door.
b. It may feel like more air is moving behind the circulation fan (between it and the back wall) than is being pushed out through the front of the heater assembly. That is because the aluminum fins of the heater greatly reduce its velocity.
c. We use fog tests to visually understand airflow in a design. Essentially, we just use a $60 fog machine from Amazon - also fun for parties!
d. I filmed a quick video of a fog test in an MV1 with a properly installed circulation fan/heater assembly (note: fan is not visible and wires come from left side) to demonstrate how the air is being pushed out through the door.

3. I put in tap water but we have VERY hard water-should I switch to distilled.

a. You do not have to use distilled water, however, depending on your goals it may be beneficial.
b. If you use tap water for other plants in your classroom, it’s probably OK to use with your MV1 too.
c. If you are trying to measure or control the number of nutrients available to your plants, it would be advantageous to use distilled or reverse osmosis-filtered water.
d. Having “hard” water is a great learning opportunity for students to learn more about water chemistry and plant nutrition by digging deeper into something that they experience every day.

  • Search Google for ".pdf" [name-of-your-city], to find a local report about your water quality. This will tell you what is already in the water - so you can know which of those “hard” nutrients are already available to your plants - before adding fertilizer. For example, I googled ".pdf" Albuquerque and was able to find this report from 2021
  • It’s also worth purchasing a couple of $15 Total Dissolved Solids (TDS/EC) meter, to compare your actual tap water to what is listed in the report.
  • You may be able to reduce the fertilizer you use (10 grams, 12.5 grams, etc.) because some of those “hard” nutrients are already in your water.

Regarding water, I was curious about the long term effects of mineral build up inside the pump unit (since it’s so small). If tap water is OK, is there a protocol about how to descale build up (maybe with dilute vinegar mixture?).

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This is something that we’ve been talking about internally and is a great point - so thanks for bringing it up!

  1. The original intent of the pump was to transfer tap water (0-300 ppm) from the bottom reservoir to the upper reservoir. All nutrients were to be delivered through a slow-release fertilizer pre-mixed into the media. Some of our pumps have been used for 4+ growth cycles over the last eight months and we have not observed any build-up around the base of the MV1 when using tap water that is <250 ppm.
  2. We have not tested whether buildup will occur using “hard water” or tap water from any other cities other than St. Louis, MO. I completely agree though that we need to test this further before we recommend the MV1 for use with hard water :zipper_mouth_face:.**
  3. @hmw sent me this photo showing buildup of minerals around the peristaltic pump. I believe this occured when he had hydroponic fertilizer solution (Jacks 20-20-20 at 1500 ppm) in the bottom reservoir. It’s possible something else went wrong though, there was also buildup all around the base of the MV1 - and even a cobweb! I have not been able to replicate this situation - or observe any buildup of minerals on my units despite using the same fertilizer. I will wait for @hmw to clarify exactly what the situation was when he observed this before speculating more :zipper_mouth_face:.


closeup of buildup around the pump of @webbhm’s MV1, after being tested with hydroponic solution.


full photo of of the brain, showing large amount of buildup on top panel next to brain

  1. @speck_c Have you observed a buildup of minerals around pumps in the past using your city’s source water? I’m going to assume given your interest in coral tanks that you’ve got some experience with buildup - haha. Have you used a diluted vinegar solution to clean a peristaltic pump before? If so, how long did you cycle it for? We could create a maintenance procedure, which would cause the pump to cycle for an hour, or something like that - definitely open to suggestions for how to keep this “low maintenance for teachers” though too - so please let me know if you think this is the right approach.

The pump apparatus is directly next to the Raspi and not separated by anything. I think it’s a safe bet that multiple rounds of fertilizer and hard water WILL drain down to the reserve water tank over time. You could develop a procedure for switching out the pump (so people don’t have to mail in the ENTIRE raspi), selling replacement pumps, or even lines of code to regulate when the pump is needed (weekends/breaks) to extend its lifespan. You will have every variety of soil, fertilizer, and water thrown in these things.

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Prints of new brain enclosures…we considered putting the pump in a separate enclosure from the other electronics but opted to just add a wall.

We understand that the pump is going to receive abuse and encourage you to push its limits. Honestly, I would prefer to learn the impact of hard water on our system rather than encourage you to use only distilled. We chose a peristaltic pump because no part of it will come in direct contact with the liquid making it very tolerant of particulates. We expect that the first point of failure will be with the hose (silicone) itself - not with a mechanism within the pump - though we have not tested any of these until the point of failure.

In response to the question: “How much power does the MV1 utilize?

The answer is: *60 watts, during “day” settings and *

Actual measurements from batch 1 (first 20 units) Value
AVERAGE of Watt Draw (5 minutes) 61.96000
STDEVP of Watt Draw (5 minutes) 1.22572
VAR of Watt Draw (5 minutes) 1.58147
MIN of Watt Draw (5 minutes) 59.20000
MAX of Watt Draw (5 minutes) 64.00000

Test Conditions…

  • Heater - Set to 90F (max) day temp and 70F night temp.
  • Ambient air conditions of 70F and 60% RH.
  • Lights - Lighting is set to 255 (max) settings for 14 hours.
  • Watts data from “Kill-O-Watt” purchased on Amazon ($25).

I’m happy to share that the new Brain and LED circuit boards exceeded our goals for max PAR. We did end up reducing the max intensity of the white channel a little bit, but the Batch 2 hardware will allow for higher red and blue intensity to be used in LED color spectrum comparison experiments.

PAR for Batch 2 - V0.6 (actual vs predicted)

Batch 1 (actual) Batch 2 (predicted) Batch 2 (actual)
White 286.3 286 204.7
Blue 14.4 ~40 97.6
Red 55.8 ~90 147.4
Far-red 2.1 ~8 3.1
(all) 363.1 ~430 448

Total Day Light Integral for Batch 2 - V0.6 (Shipping 04/27/2023)

mol of photons per meter per day at germination height in the center of MV1

8 Hours 12 Hours 14 Hours 16 Hours 24 Hours
White 5.90 8.84 10.32 11.79 17.69
Blue 2.81 4.22 4.92 5.62 8.43
Red 4.25 6.37 7.43 8.49 12.74
Red & Blue 6.94 10.41 12.15 13.88 20.82
All @ Max 12.93 19.39 22.62 25.85 38.78