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Hi i was wondering what sort of relays that is good using with the 30A Electrolize with external relay option speedos and how big relays you could use,for example if i use a relay that can handle lets say 50A continiously, could the speedo be able to work with that or shall the external relays be rated at 30A continiously?
Technobots sell some that are sutiable
http://www.technobots.co.uk/en-gb/dept_31.htmlhttp://www.technobots.co.uk/en-gb/dept_31.html
Ed
http://www.teamstorm.comhttp://www.teamstorm.com
Thanks but if i take a 40A relay, can the rest of the speedo handle the current?
2.Or shall the relays be maximum 30A?
3.Is it the sort of relays that are in cars?
what motors you running?
Danny
Our 30A controllers using the relays provided with them were quite capable of handling peak currents of over 100 amps when trying to push the workbench through the workshop wall.
Sadly the 7.2v motors at 13V+ on a fully charged SLA tended to get a little warm ;(
regards
Tim
Ok but for how long did u try to push it? I havn´t built a robot yet but I will use some cheap 18V drillmotors for the drive, 900rpm, 3:1 reduction @ a 25cm/diam wheel and I want the speedos to survive the motors being stalled when pushing robots and such things. Because I´ve heard that some drillmotors get stall currents of about 40A and that would be quite dangerous for the 30A electrolize or?
No.
Electrolises can handle more than 30A once the relays are capable of handeling the current. I am using 15amp electrolises with 40amp relays without a problem.
Regards
Ian
OK so it is the relays that handles the current? Does that mean that i could use 100A relays on a small 15A electrolize without frying the speedo?
the FETs supply the current, the relay is used to change the direction. I think the FETs are capable of about 90Amps peak, the controller is mainly limited by the relays (hence why people change them).
Ah ok but what about the continious current the FETs can handle?
I may be a cynical here, but vould it be so simple that its 15A for the 15A version and 30A for the 30A version?
Seriously, you didnt really have to ask that.
What I mean is if my robot should be standing pushing against another robot for 10 seconds, that would generate more then 30A and not just 1 peak over 40A? That makes me wondering if an electrolize could handle more then 30A for a couple of seconds?
why would you stall your motors for 10 seconds? as soon as you stall you should pull off the power, you speedos may take it, but your motors wont.
I dont intend to stall them in 10 seconds but when 2 robots are trying to push eachother one must win and during the time they push the motors draw extra current, you shouldnt back away all the time to avoid getting into pushing or? Then you dont get good at agressivnes if it goes to the judges...what i mean is that it must be able too stand up to a bit of pushing robots around and such
but the point is they shouldnt stall for that long, youre motors wont be turning when stalled so you cant move so you have to back off the power.
Ive always had pusher feathers (about 3 1/2years now) so i know what to do during fights. If youre that worried about stalling then get a controller with current limiting (although be prepared to pay at least £140).
If your motors are powerfull enough to push a robot, the chances are your wheels will spin before stalling.
ok, i thrust you, what motors are you using?
Is it me, or was that a bit intimate for a public forum?
(Thank you, just as I was falling asleep.)
--
Fluppet
lol, ive been running golds for the past year in Alpha.
ok
You use 15A controllers as well, dont you?
yeah 15amp non-modded controllers. I have blew a relay in each, but i dont consider that bad as the controllers are over two years old and they get a hell of a thrashing!
hmmm......isnt it esier to make your own speedcontroller?
Many try .... most buy.
From what Ive read ...It aint as easy as it first appears.
Cant recommend it Joacim, based on my own experience. Unless you find making a speed controller interesting in its own right, its probably not worth it.
But whats the problem with doing your own speedcontroller? Lack of control? I´m doing it because its way cheaper then buy a new one!
Itll take a lot of time and effort to build your own speedos. Im working on a fether speedo as well. Right now, the schematic is almost done. Meaning I still have to work out some details, this can take up most of your time. Im hoping it will fit the size of the PCB I usually use (half a eurocard). The layout stage wil probably take a long time aswell.
In the end, I may see the first versions go up in smoke if I made a mistake. Im keeping my fingers crossed.
So its probably not cheaper, because youll probably blow up the fist few versions and it will take a long time to get it working properly.
The main hrudles are getting the timing of the fets right and current limiting.
But I´m gonna use a servo and another guy is doing the job for me :)
Yes, but he planned on using ordianary automotive relays and the PCB from a servo. So I guess there wont be much that can go wrong, but hell lack a bit of controll with only one speed.