| Electronics > Projects, Designs, and Technical Stuff |
| JBC-mini - a low cost T245 handle controller |
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| dom0:
With a floating heater supply a standard N-Ch MOSFET should do the trick, given that the heater supply (and thus Vgs) is only floated by thermovoltage |
| poorchava:
The switching element has to have a high off-state impedance, because the switched end of the heater is the thermocouple connection at the same time, so a slightest current flow will throw off the measurement, as the thermocouple is not particularily sensitive (like 2.8-3mV @ dT=300 deg.C) the amplifier has really high gain (in the order of several hundred). The floating gate drive storage capacitor is fed through the parasitic body diodes of the mosfets, so the temperature measurement must occur near zero-crossing, because at that moment the charge pump does not draw current through body diodes, and also interferences are at their lowest. |
| fredboivin:
Hi, very interesting project! Do you know how JBC does its sleep and tip changing poweroff? In the UniSolder, Sparkybg does it with an IR sensor, but I'd like to know how has JBC implemented it. Thanks! |
| savril:
--- Quote from: fredboivin on June 04, 2015, 07:41:03 pm ---Hi, very interesting project! Do you know how JBC does its sleep and tip changing poweroff? In the UniSolder, Sparkybg does it with an IR sensor, but I'd like to know how has JBC implemented it. Thanks! --- End quote --- Watch Dave tear-down video on the JBC. The iron holder has a wire that get it linked with the base station. When the iron is in the holder, the iron touch a metallic surface. So it is as simple as detecting that the metal in the holder is connected to ground. When you see that other shops are using accelerometers for that :-DD. For the tip, it detect that there is no resistance (by current measurement ?). In Sparkybg design, he use the resistance to differentiate the different irons and it also detect the tip changing (but for JBC it's not named tip but cartridge because it contain the heating element). |
| fredboivin:
Ahhhh, I must have missed it! I should have known a reputable company like JBC would keep it stupid simple. But, isn't the cartridge at 180degC? How do they keep that wire from heating up? Thank you very much! |
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