I have a device I'm developing that interfaces with an existing consumer device. I can't change the design of the existing device and it has a poor design with how a battery is connected to it. It doesn't come with a battery so they leave it to the customer to source. A very common and good choice is a 2 cell LiPO battery. Unfortunately, the input connector of the device is identical to the common 2 cell LiPO balance cable, but wired completely different. People see the same connector, plug it in and poof.
So I would like to make a tiny board that will plug into the device's socket and provide an identical socket for the user to plug their battery in to. The goal being that it would not allow current through (and will not be damaged itself) in the event it is wrongly connected.
Ideally the tiny board would have a green and red LED to indicate if the battery is in right.
On the original device, we're dealing with a 3-position socket with the middle being +ve and the two outer are -ve (joined together). The battery then is intended to use a 3 position connector where only the middle and one outer are used, but if a 2 cell balance connector is used there would be 3 wires (one at +7.2V, one at +3.6V and the other at 0V). So I guess that's 12 possible combinations mathematically but 5 would never happen (due to how balance plugs are designed). That leaves 7 combinations, 2 of which are correct. I need to protect against the 5 that aren't.
Below I have the possible/likely combinations. G is 0V, H is a positive voltage. The last one has L, which is in the event this is a balance plug (which should not be used but customers can be ignorant and/or careless) and is also a positive voltage, half of H. X is not connected.
G H X - Good connection
X H G - Good connection
H X G - Battery short
G X H - Battery short
H G X - Reverse Polarity
X G H - Reverse Polarity
G L H - I don't even know what to call this. Battery is shorted and device is powered?
I really don't know how to go about this. My experience is pretty much limited to circuits where it is a given that power flows the way it is supposed to. I get how to protect against reverse polarity. I'm fuzzier on short circuit protection. I really have no idea how to handle that last event.
Thanks.
So I would like to make a tiny board that will plug into the device's socket and provide an identical socket for the user to plug their battery in to. The goal being that it would not allow current through (and will not be damaged itself) in the event it is wrongly connected.
Ideally the tiny board would have a green and red LED to indicate if the battery is in right.
On the original device, we're dealing with a 3-position socket with the middle being +ve and the two outer are -ve (joined together). The battery then is intended to use a 3 position connector where only the middle and one outer are used, but if a 2 cell balance connector is used there would be 3 wires (one at +7.2V, one at +3.6V and the other at 0V). So I guess that's 12 possible combinations mathematically but 5 would never happen (due to how balance plugs are designed). That leaves 7 combinations, 2 of which are correct. I need to protect against the 5 that aren't.
Below I have the possible/likely combinations. G is 0V, H is a positive voltage. The last one has L, which is in the event this is a balance plug (which should not be used but customers can be ignorant and/or careless) and is also a positive voltage, half of H. X is not connected.
G H X - Good connection
X H G - Good connection
H X G - Battery short
G X H - Battery short
H G X - Reverse Polarity
X G H - Reverse Polarity
G L H - I don't even know what to call this. Battery is shorted and device is powered?
I really don't know how to go about this. My experience is pretty much limited to circuits where it is a given that power flows the way it is supposed to. I get how to protect against reverse polarity. I'm fuzzier on short circuit protection. I really have no idea how to handle that last event.
Thanks.