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What in the world are You going to drive with such current?
And what are You going to use as a power source?
Two motors that require 19.2 Amps each at 24 volts, Then a total of 5 amps of other electronics at 12 volts. This is fed by a DC-DC converter that outputs 10 amps 12 volts. So I was thinking 45 amps would be safe in case of any current spikes.
Get an automotive 24V relay that can handle at least 50A.
Then use any switch you like to switch the relay.
Automotive fuses at the positive terminal of your battery is cheap and a really good idea - one fo each circuit (at least a large current fuse for the motors and a low current fuse for the rest).
Could I use a 24V 40 amp relay such as this one because the only electronics that are running at 24 volts is the motors and I just read that the motors actually run at 18 amps each. All of the other electronics run at 12 volts. On the second link it says the max continuous current is 50 amp. Do you think I'll be ok?
I am not too familiar with relays so how would I hook up a switch and how would that work?
QuoteAutomotive fuses at the positive terminal of your battery is cheap and a really good idea - one fo each circuit (at least a large current fuse for the motors and a low current fuse for the rest).I am using the Sabertooth motor driver so it does have protection against current spikes and I am using the Axon II which also has current protection.
Swell, but you still need fuses - to protect you, your home and your electronics!I'm sure there's something along the line of "Fuses... We don't need no stinkin' fuses" in some collection of Famous Last Words
If I were to use two relays, I would need two 20 amp relays, right?
Also, would I put this in between the Sabertooth and each of the motors if I was using two relays?
What switch what I need then? 10 amps?
Would I need diodes able to hand 20 amps then?
And would I just put the diode in between the diode leads or am I reading that incorrectly? I have never used a diode for this purpose so I am not sure how I would rate it.
Ps: Sorry for all of the questions
They are best placed before the Sabretooth, i.e. right after the 24V battery, but the relay contacts just replace a mechanical switch, so anywhere you would place a switch (wheter one or two relays are used).
If I were to use two relays and connect them before the Sabertooth, how would I do that? What would be the point of the using two if your not even connecting them to each motor?
Now I'm thinking - if You use Sabertooth , why the bloody hell do You need switches? Just have one main switch at the battery end of Your circuitry.
Because I cannot find a 50 amp switch.
Does the Sabertooth somehow cancel out the 38 amps of the motor?
I believe Soeren just explained how to use relays for what You need.
What? That doesn't make any sense. I asked a question about how to use the relays and you tell me to use just one switch and then you tell me Soeren explained how to use the relays.
I still dont understand how that would work if I put the relays before the Sabertooth. Why would you use two switches for the Sabertooth? What would be the point of the using two if your not even connecting them to each motor?
Ok, confusion is taking over. In Your previous post You mentioned that 50A switches are hard to find, hence I reminded that You can use automotive relay with with small switch to controll it (as Soeren adviced).
f You put relay as main switch, then it is placed just after the battery and You need only one. If You want to switch (ON/OFF) every motor separately, two relays are added - one relay in series with one motor (between motor and Sabertooth).
QuoteThey are best placed before the Sabretooth, i.e. right after the 24V battery, but the relay contacts just replace a mechanical switch, so anywhere you would place a switch (wheter one or two relays are used).If I were to use two relays and connect them before the Sabertooth, how would I do that? What would be the point of the using two if your not even connecting them to each motor?
What do you think about a light switch? I saw one at Home depot that was rated 30 amps at 120 VDC. That has to be able to withstand40 amps at 24 volts.
I'm not sure how to calculate the amperage the switch would be rated at for 24 volts.
Don't count on it...The voltage rating of a switch is about isolation.The current rating starts out as a power rating, but since the (max) contact resistance is known, the current can be found by the formula: I=sqr(P/R)Assuming that the 30A switch has got a contact resistance of say 0.01 Ohmn (10 mOhm), any voltage from 0.3V up to whatever voltage the contact separation allows without flash over will dissipate the same power (9W in this case).The only difference you'll see is when switching and switching an inductive really lowers what a contact can handle, but at least you can switch with no power going to the motors and then you're in the clear as long as the contacts are rated for a fair bit over the anticipated current.
You could do away with the switch by using the fuse as switch - just get automotive fuses of the type that connects to spade terminals.
How would you use a fuse as a switch?
This got me thinking about circuit breakers. Are there any issues that I would have to worry about with these? Will they wear out very fast over time though?
I still do not understand why relay is not good enough solution?
Can you guys verify this issue I'm having with what spade terminals to I should solder my diode to?
Here is the information it gives on the relay; "3/8" spade terminals for the switching contacts. The coil connections use 1/4" spade terminals."
Where do I solder the input and output, the 3/8" terminals?
I just want to verify this diagram with you guys before I begin to solder. The "bar" (cathode) on the diode goes on the positive terminal (terminal 85) of the relay, right? Here is my diagram.
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Started by madsci1016
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