Power source.pdf (3.5 MB)
Hello nils,
Maybe one of the engineers can help with this.
My first thought is, when you activate the 12V, 3A coil, is it just taking so much power, that there is not enough for the transmitter to stay active? How much current is need by the transmitter, and how much power is supplied by the power supply?
Either way, more information will be needed. Do you have a part number for the transmitter and power supply?
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It looks like we are burning out the transmitter. It no longer turns on after we activate the button controlling the coil. None of the power LED lights come on, it is none reactive to anything we do after we push the coil button.
The coil is 12 volts 36w, but we are using a 20 volt power source. So i think that is increasing the flyback spike.
You may be overpowering the coil and transmitter. If you provide more detailed information for each part of your schematic, like part numbers, photos,… It may help for an engineer to determine a possible solution.
Not an especially picky sort of application; most anything out of the 1N400(x) series could be a reasonable starting point.
Further information relating to the topic is mentioned in this post and likely others. While improvement is quite likely, additional/different measures may or may not be needed. It can be difficult to carry on a phone conversation if somebody else in the room is firing a cannon at random.
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Thanks Rick, does it matter that we are switching the ground and not the power side? Would it be better if the switch was on the + side?
By bridging between how does the diode stop the current from returning back down the + side?
It’s generally more common to switch the (+) side, because many systems have a connection between supply negative and the chassis/enclosure. Switching loads from the “hot” side in those cases reduces the number of possible bad outcomes in the event of a wiring fault. Effects relating to your radio might vary and come with more nuance, but aren’t worth worrying about as long as there’s an elephant in the room.
I’m not sure what your mental picture looks like to be able to answer the question as posed.
Your solenoid is an inductor. Inductors resist changes in current flow in much the same way that an object with mass resists changes in velocity. Opening the switch causes an abrupt change in current flow, and is akin to stopping one’s bicycle by riding it into a brick wall. Fast and effective, but it usually ends with things breaking…
The diode provides a path for current to recirculate through the coil when the switch is opened, letting the energy in the coil dissipate slowly. The result is similar to stopping one’s bicycle by simply not pedaling. Though much less painful by itself, it takes a lot longer and in the wrong circumstances ends up hurting as much as the wall. It’s very simple to do though.
Other methods described in the linked resource can be compared to stopping one’s bicycle by applying the brakes. Done right it can offer a happy middle ground between the other two options, done wrong and one still ends up with the unpleasantness of one or the other. It’s more complicated in any case.
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