Would anyone here who is apt in circuits and electrical engineering be willing to help me set up an electromagnetic field? I’m currently conducting a masters in Horticulture at MSU and may be interested in looking at magnetoprimed seeds. From what I can find it seems people use something called a helmholtz pair. I have absolutely no experience in circuits and electrical systems so if anyone more experienced could lend me a hand that would be so cool.
Thanks!
I had to look up what a Helmholz pair is, but that seems like something we can build. Do you know what range of field strength you want, and physical size? I assume for seeds you just need something pocket-sized.
We have a benchtop constant current supply, which could get you started. You’ll of course need some magnet wire (I think we have some), and a form to wind it around. One thing we don’t have in the shop is a Teslameter to measure the actual field strength. If you can obtain one of those, this seems feasible.
I’m happy to chat with you about this any time.
Hello,
Sorry for the late reply, I didn’t get a notification for this for some reason. That sounds great! I’ll be in over this week’s open hours working on some stuff at the woodshop so we can chat about it then (will be in today until around 7). I can look into some other references for specifics. Thanks!
I’ll be in tonight around 6:00pm. I’m coming to do drop-in woodshop checkouts, but if nobody wants one I’ll be free to talk with you.
Hi @Akane_Takenaka,
Late last night I had a chat with Claude AI about building a Helmholtz pair that could create the field strength you’re looking for, and it looks quite feasible to build something, with a controller using parts we mostly already have. I hope you don’t mind me doing this; it’s an interesting little design project.
Since you’re working with seeds, I’m picturing something fairly small, like a coil diameter of 10cm, with 5cm space between. A simple coil form could be a piece of PVC pipe, or a pipe coupling. It turns out that a coupling for 3" (nominal) PVC pipe has an actual O.D. of 4", or 10.16cm, and is 10cm long, so that’s promising. You could wind two coils on that, 5cm apart, and maybe drill some holes between for access to the inside. Or use two pieces mounted in come kind of frame for unrestricted access to the space between the coils.
There are several interrelated variables to think about – diameter, wire size, number of turns, the current required, the power supply voltage needed, and the temperature it will get to. Claude came up with a nice calculator with sliders to vary the radius, no. turns per coil, and target field strength, and then shows the current and voltage, power dissipated, etc.
Here’s a link to the chat: Claude. Unfortunately if you don’t have an account, you can’t see the calculator or the diagrams. But I think with even a free account you can log in and see them. (I asked it to make circuit schematics and got some nonsense, but the block diagrams are sensible.)
Here’s what I’m imagining: a microcontroller like an Arduino or ESP32 with a Hall effect sensor to measure the field strength, and an analog output going to a current driver. The MCU continuously adjusts the current to keep a constant field, over hours / days / weeks. At higher field strength, it’s going to get hot, so maybe a temperature sensor and fan.
With a fancy controller using an ESP32, which has WiFi, you could go over the top and build a web interface so you could control it from a laptop, and have it log the field strength, temperature, etc. and show you a graph. If you don’t want to do that much programming, an Arduino Uno could keep it at a set field strength without much coding. (These days, you don’t have to do the coding, you just need to ask your AI friend the right questions.)
Here’s what you’d need for something like this:
So it all seems feasible on a grad student budget. If you want to go down this path, I can help flesh out the current control circuit.
Carl