We have a system running on 4 12V batteries that fires a 48V power supply. The logic to fire the power supply is a 5V signal but the power supply needs a 24V input signal to fire. I am looking for a another device that will convert the 5V to 24V but we need the response to be as fast as possbile. We will be firing the power supply at least 10 times a second and I'd like to shoot for 20 times a second but the less time it takes to get the fire signal the better (obviously). I was thinking we could use a solid state relay and use 2 of the batteries to get the 24V power supply input fire signal. I would think the SSR would be the fastest response time we can get. I was looking at the one from sparkfun below:
If you look at the comments, it looks like there are multiple issues with that one so I am uncomfortable getting that relay. Cost isn't an issue here, we want a FAST, reliable and safe way of doing this. If we can adjust the "delay" in the output that would be great too! We will need to protect the input port of the power supply so we would need to current limit the 24V output to the power supply.
I am looking for a another device that will convert the 5V to 24V but we need the response to be as fast as possbile.
That "device" is a transistor that turns on or off the 24V power that you already have.
Yep, they are fast.
We will be firing the power supply at least 10 times a second and I'd like to shoot for 20 times a second but the less time it takes to get the fire signal the better (obviously).
Transistors can switch 10's of thousands of times per second.
So the collector would be our 5V input and then we would connect the base to the 24V battery and the emitter to the power supply fire signal?
The collector is what triggers the transistor as a switch, so it gets connected to the control signal - the digital pin that gets set HIGH to fire.
The base is where the current to be switched comes from - the + side of your 24 volt battery.
The emitter goes to the device to be powered when the transistor is switched on.
No, no, no!!! Do that and you are likely to burn out the transistor, the Arduino, or both.
There are 3 configurations in which a transistor can be used: common emitter, common base, and common collector (also called emitter follower). None of them correspond to the above. The most commonly used (which is almost certainly what you need) is common emitter, as follows:
The BASE is what triggers the transistor as a switch, so it gets connected to the digital pin that gets set HIGH to fire - through a series resistor to limit the base current.
The COLLECTOR is where the current to be switched comes from. In your case this will be +24v through a pullup resistor.
The EMITTER goes to common ground (i.e. Arduino GND and the -ve side of your 24v battery).
Note that this configuration will give you +24v to the power supply when the digial output is low (or the pin hasn't been configured as an output), and 0v when it it high. The pullup resistor to +24v will limit the current going into the PSU, which may provide the limiting function that you need on the PSU inport port. If having the PSU input high when the Arduino is unpowered is a problem, this can be fixed using a second transistor.
I agree that the transistor is better than a solid state relay here. But let me ask one question and make one point.
The question is: how much 24V current does the power supply input need to "fire"? Since you want to limit the current, it sounds like not much is needed. Do you know exactly?
The point is related. For smaller currents, a transistor like a BC337 should work. They cost about 7 cents. I've been working on a similar application, and could draw up a schematic for you.
But if you need too much current, say over 1 Amp, a solid state relay may be better. The one you found at Sparkfun won't work. It's for AC loads only. Since you are using batteries, you need a relay that handles DC loads. Futurlec has one for about $20 that would work well. www.futurlec.com/Relays/SSRDC100V40A.shtml It will handle up to 40 Amps.
There are advantages to solid state relays. They usually actually consist of 2 transistors so that the polarity doesn't matter. Like previously mentioned, speed will not be an issue. For simplicity, you could use an N-Channel FET. Pick a logic-level gate to ensure full turn-on. You can use it in a low-side switch config.
Well...its very easy man. Dont need any circuits!!!!
Use ELECTROMECHANICAL Relay!!!
Operating Voltage Range: 5-12V
Max. Output(you can connect):120-240V.
Wiithout the specs for your power supply we are only guessing how to switch it - you say 24V, but what current? How long a trigger pulse (or is it continuous?) Can we derive a 24V supply from halfway along the battery chain? Do you have a link for the specs for this strange rapidly switched power supply?