I wanted to create a simpler imitation of what is primarily a graft heating mechanism for nuts or grape grafting. One part at a time starting with the brown heat trace wire to the left which is wrapped to heat the sensor and the sensor itself is kind of a replica of a dormant graft and as actively demonstrated the rise is 30F.
<----- indoors ---
Note that this plus 30 degrees is the maximum value temperature in a control loop because underneath the green tape I adjusted the setpoint beyond the reach of our target temperature.
The small blackbox transformer is actual repurposed here from a 6 volt motorcycle battery charger. without the battery the output voltage keeps to within 7.2-7.5 volts and can adequately and very nicely feed up to 5 other 130 ohm brown heating wires. (more on materials later) The actual watts being loaded per wire wire is just under 0.4 watts which (engineering purposes) is roughly equivalent to my multimeter reading of ~52mA.
Another few design accomplishments (pros):
-no fluid, pumps etc. are involved in this one, but this is only beneficial for home purposes for several grafts a few at a time. Volume propagators will find patents that have already been established that cover heat/fluid systems better.
Disadvantages:
-since this will be done for mostly topworking purposes the wind is at some disadvatage here. For example when I forced air over the desk the temperature rise reduced to only +10F (~33%). This may not be an issue depending on your programmed range of target. Teflon tape application around the brown wire as an idea would stand up well to calm wind losses.
Materials: The Inkbird is kind of the command center. I use a wifi one which costs more than the exact same thing online by Inkbird for ~30 dollars. That's the biggest cost here. I will cover the basics of manufacturing the next most pricey item next.
The same brown wires at 13 inch lengths weigh in just right at ~130 ohms. They are not costly in and of themselves but due to the nature of the supplier I can't release which part or where to get what needs to be procured. In the case a manufacturer gets interested I would have no issues as long as I'm contacted privately. Those that I know that either want to borrow these inexpensive graft or cutting wrapping devices can use a few. To any interested parties then read on...
These won't last as long as they would were the cotton like materials inside to get wet so the best idea is vaseline or toilet bowl wax for keeping up with the final coating. I would recommend this just even on top of any parafilm (stated teflon by mistake) that may be put over top as explained above.
For any who seek other products and need to go elsewhere then understand that the chromium conductors are in need of soldering to a solder wick copper. This is the determination that really adds onto the material costs of each because a magnification and holding device become necessary, not to mention the wick and solderer etc. The reason why is seen here that the ends to grab are as small as hair;
Brown wire ends Closeups
Sandpapering nichrome wire at the intended soldering points is often recommended.
Perhaps there are small crimp-type connectors commonly available that would reliably connect
mechanically to the wire; especially if the wire end was folded over several times to increase the effective diameter.
Various Molex connectors are inexpensive.
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