Some of you may be familiar with these, but for hobby-class electric radio-control vehicles, many people use a small switchmode regulator (called a BEC for Battery Eliminator Circuit) to efficiently regulate various battery voltages from 11.1v (3s lipo) up to and over 42v (10s lipo) to provide 5v/6v @ 3A+ to power servos and the radio receiver. Linear regulators would be far too wastful. Here are a few examples of such circuits we use:
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Anyway, these switch mode regulators have the unfortunate characteristic where they can fail, and when they do, can output the full battery voltage. This is "not good" for the 6v servos and receivers, both of which can run over $100 each. So, I was thinking of making a small and cheap catastrophic safety circuit that can be added to the output to keep this from happening. Size and weight in these vehicles is a concern, so the device has to be small and light. I've been toying around with a few ideas. Two of my favorites are:
- Use some type of shunting device (like a TVS or Zener diode) rated for around 6.5v. Hook this to the output via a fuse. If the BEC fails and outputs full battery voltage, the TVS would shunt the extra energy to ground, and thereby blow the fuse.
- The other idea uses a comparator that cuts the output when it exceeds a set value, probably 6.5v. This method is less destructive, but a little more complex (and therefore more prone to fail) and I am concerned about the response time.
Yeah, the BEC is still toast in either of these solutions, but at least we've saved the expensive stuff downstream.
Obviously, the best solution would be to have these makers put some type of protection in their products, but until they do, we have to do what we can.
Any ideas, suggestions, comments?
Edit: Sorry, I just realized I might have posted this in the wrong area...
- **broken link removed**
- **broken link removed**
Anyway, these switch mode regulators have the unfortunate characteristic where they can fail, and when they do, can output the full battery voltage. This is "not good" for the 6v servos and receivers, both of which can run over $100 each. So, I was thinking of making a small and cheap catastrophic safety circuit that can be added to the output to keep this from happening. Size and weight in these vehicles is a concern, so the device has to be small and light. I've been toying around with a few ideas. Two of my favorites are:
- Use some type of shunting device (like a TVS or Zener diode) rated for around 6.5v. Hook this to the output via a fuse. If the BEC fails and outputs full battery voltage, the TVS would shunt the extra energy to ground, and thereby blow the fuse.
- The other idea uses a comparator that cuts the output when it exceeds a set value, probably 6.5v. This method is less destructive, but a little more complex (and therefore more prone to fail) and I am concerned about the response time.
Yeah, the BEC is still toast in either of these solutions, but at least we've saved the expensive stuff downstream.
Obviously, the best solution would be to have these makers put some type of protection in their products, but until they do, we have to do what we can.
Any ideas, suggestions, comments?
Edit: Sorry, I just realized I might have posted this in the wrong area...
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