Project Update 04-06-04
Speed Controller Modding.
I got another 12V bat. from Surplus Center to juice the bot up to 24V. I started getting worried about burning up the speed controller at this point. I did a little math and realized that I was fine unless the robot stalled itself at full power somehow for for than 5-10 seconds or so. In case you didn't know, electric motors draw more and more power as they meet more resistance to movement. If you lock down a motor so that it cannot move it will draw its internal electrical resistance is at its lowest and thus its current draw is at its highest.
To help get rid of some of the heat that the speed controller might build up during lots of heavy use, I decided to add a heat sink and fan. It is probably not really needed but I was bored and it just looks cool :)
Another thing that prompted me to do this was that I noticed the controller was in pretty bad shape. Its my brothers and its expensive so I dont want to screw it up. Its rated for 30Amps cont. or 60A for 5 seconds. Right now my motors are pulling about 6 or so at no load but when you lock them down they probably pull about 24Amps! At 24 Volts that would be 48 Amps if locked down. Well under the 60 max but well above the 30Amp cont. level.
I took a shot of the crap leaking out of the capacitors in the speed controller. There was even a spider nest in there.
(Note: Later on I learned that this isn't leaking caps. Vantec said it was a glue they use. *shrug*)
I hooked up the Land Raider and played with it a bit and felt the heat on the controller box, it wasn't much and the metal box seemed to be doing pretty well at sinking it. However I figured I'd stick my heatsink/fan on there anyway because it would look cool and better safe than sorry etc. The power mosfets were all resting against a heat pad that was stuck on the top of the metal enclosure. I put some heat sink grease on them and it should make a big difference because not all of them were touching the pad very well.
I found an old processor heatsink that fit pretty well. And by coincidence its made by Vantec, the same name but different company that makes the speed controller. I polished up the case top and sink bottom with some sand paper and drilled holes in the sink to match the controller box.
I greased the heck out of this as well and then mounted the sink.
Then after finding new screws that were long enough I bolted it down and put the fans back on. At 12V they draw about .2 amps, I think I'm gonna either just run them off the 6V battery that I'll be using for the servo controller or at least put a resistor to slow them down a little because they really are overkill. Just the sink and grease alone probably made a huge difference.
I got another 12V bat. from Surplus Center to juice the bot up to 24V. I started getting worried about burning up the speed controller at this point. I did a little math and realized that I was fine unless the robot stalled itself at full power somehow for for than 5-10 seconds or so. In case you didn't know, electric motors draw more and more power as they meet more resistance to movement. If you lock down a motor so that it cannot move it will draw its internal electrical resistance is at its lowest and thus its current draw is at its highest.
To help get rid of some of the heat that the speed controller might build up during lots of heavy use, I decided to add a heat sink and fan. It is probably not really needed but I was bored and it just looks cool :)
Another thing that prompted me to do this was that I noticed the controller was in pretty bad shape. Its my brothers and its expensive so I dont want to screw it up. Its rated for 30Amps cont. or 60A for 5 seconds. Right now my motors are pulling about 6 or so at no load but when you lock them down they probably pull about 24Amps! At 24 Volts that would be 48 Amps if locked down. Well under the 60 max but well above the 30Amp cont. level.
I took a shot of the crap leaking out of the capacitors in the speed controller. There was even a spider nest in there.
(Note: Later on I learned that this isn't leaking caps. Vantec said it was a glue they use. *shrug*)
I hooked up the Land Raider and played with it a bit and felt the heat on the controller box, it wasn't much and the metal box seemed to be doing pretty well at sinking it. However I figured I'd stick my heatsink/fan on there anyway because it would look cool and better safe than sorry etc. The power mosfets were all resting against a heat pad that was stuck on the top of the metal enclosure. I put some heat sink grease on them and it should make a big difference because not all of them were touching the pad very well.
I found an old processor heatsink that fit pretty well. And by coincidence its made by Vantec, the same name but different company that makes the speed controller. I polished up the case top and sink bottom with some sand paper and drilled holes in the sink to match the controller box.
I greased the heck out of this as well and then mounted the sink.
Then after finding new screws that were long enough I bolted it down and put the fans back on. At 12V they draw about .2 amps, I think I'm gonna either just run them off the 6V battery that I'll be using for the servo controller or at least put a resistor to slow them down a little because they really are overkill. Just the sink and grease alone probably made a huge difference.
