Tweet
Re: UK Kilobots - 1.362kg (3 lbs) Combat Robots
Right, so just making sure I understand this properly (not necessarily for this, just that it's good to get an idea on how to size the fuse for future reference):
- If everything is sized correctly and runs at a lower current than the battery can deliver then there is not too much of an issue with the fuse. Meaning that the fuse doesn't need to be selected for overload on the equipment.
- In the event of a short circuit or motor stall where the current can become considerabley higher than the battery output for long durations then the battery needs to be disconnected quickly to avoid damage etc.
- The fuse needs to be sized pretty much to the maximum output of the battery (in this case 16A output=15A fuse) BUT considering that the fuses do not blow quickly at their rated current it's necessary to de-rate them so they will blow relatively quickly and disconnect the battery ASAP.
Had a look at the data sheet for the fuses and it is relatively clear what you say about automotive fuses:
http://octopart.com/atc-10-cooper-12063#datasheets (Click on link to AT10 data sheet)
Seems that a 10A fuse would take about 1 second to disconnect at about 18A, with a 5A fuse taking 0.1second at 15A.
May start off with a 5A fuse as the drive motors draw nothing and in reality once the motor is up to speed for the spinner then the current draw on that should be minimal. Quite shocking actually as a 15A fuse doesn't seem like it would blow at anything less than 20A and even then it'd take almost ten seconds.
Originally posted by mr_turbulence
- If everything is sized correctly and runs at a lower current than the battery can deliver then there is not too much of an issue with the fuse. Meaning that the fuse doesn't need to be selected for overload on the equipment.
- In the event of a short circuit or motor stall where the current can become considerabley higher than the battery output for long durations then the battery needs to be disconnected quickly to avoid damage etc.
- The fuse needs to be sized pretty much to the maximum output of the battery (in this case 16A output=15A fuse) BUT considering that the fuses do not blow quickly at their rated current it's necessary to de-rate them so they will blow relatively quickly and disconnect the battery ASAP.
Had a look at the data sheet for the fuses and it is relatively clear what you say about automotive fuses:
http://octopart.com/atc-10-cooper-12063#datasheets (Click on link to AT10 data sheet)
Seems that a 10A fuse would take about 1 second to disconnect at about 18A, with a 5A fuse taking 0.1second at 15A.
May start off with a 5A fuse as the drive motors draw nothing and in reality once the motor is up to speed for the spinner then the current draw on that should be minimal. Quite shocking actually as a 15A fuse doesn't seem like it would blow at anything less than 20A and even then it'd take almost ten seconds.
). As I recall, tas soon as you remove the current the swelling of the cell stops meaning that if it hasn't exploded by then, it wont. Apart from that short circuit currents aren't good for stuff like speed controllers, receivers and stuff.
Comment