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FRC4ME
05-08-2010, 03:15 PM
My team is building a digital circuit (more details to come later ;) ), and one of the "cool" factors of the project is that we want to only use items that are in, or have been in, the FRC KoP. In one part of the circuit we need some double throw switches (e.g. to switch a connection between 12 V and ground). Does anyone know of a current or previous KoP component that can act as a double throw switch?

The limit switches of recent years would work, but we don't have enough of those. The limit switches from previous years are only single pole. We also tried out the red light sensors, but those also appear to be single pole.

Tristan Lall
05-08-2010, 03:36 PM
How much current?

FRC4ME
05-08-2010, 03:48 PM
How much current?

Enough to trigger the control coil of a Spike relay.

apalrd
05-08-2010, 03:50 PM
A Spike needs 5v, not 12v, for the trigger input.
You can get that from the Digital Sidecar or the Camera supply on the PD board.

FRC4ME
05-08-2010, 04:05 PM
A Spike needs 5v, not 12v, for the trigger input.
You can get that from the Digital Sidecar or the Camera supply on the PD board.

I guess I should explain more. We're using the Spike relays to build logic gates, connecting the outputs of some relays to the control inputs of others (fortunately, they work at 12 V as well as 5 V). In the end, it will be a four-bit adding machine constructed of 24 Spike relays (learning about how digital circuits work :) ), the result of which will be displayed using the fluorescent green camera lights from 2007.

We also need something to act as a user input to the circuit. The user needs to be able to switch this input between 12 V (a logical 1) and 0 V (a logical 0). Since we've managed to use only KoP components up to this point, I'm wondering if we can find another KoP component to do this job, just for the fun of making a complete computational circuit out of nothing but KoP components. The cRIO, sidecar, and power distribution system aren't involved at all here.

Thanks for the help. :)

PAR_WIG1350
05-08-2010, 04:25 PM
I guess I should explain more. We're using the Spike relays to build logic gates, connecting the outputs of some relays to the control inputs of others (fortunately, they work at 12 V as well as 5 V). In the end, it will be a four-bit adding machine constructed of 24 Spike relays (learning about how digital circuits work :) ), the result of which will be displayed using the fluorescent green camera lights from 2007.

We also need something to act as a user input to the circuit. The user needs to be able to switch this input between 12 V (a logical 1) and 0 V (a logical 0). Since we've managed to use only KoP components up to this point, I'm wondering if we can find another KoP component to do this job, just for the fun of making a complete computational circuit out of nothing but KoP components. The cRIO, sidecar, and power distribution system aren't involved at all here.

Thanks for the help. :)

put the servo jumpers from the digital sidecar on pwm cables to activate the coils, or use some other, similar kop part (such as a breakers on the pd board,)
The pd board could be used as a switch board, with out the crio or the sidecar. The breakers are just completing the circuits

Al Skierkiewicz
05-08-2010, 07:49 PM
FRC,
You should do some investigation into pullup resistors. The input circuit of the Spike is a opto isolator so a pullup to 5 volts (or 12) would set the relay in one direction and a short to the common terminal would turn off the opto isolator and set the Spike for the other direction.

DonRotolo
05-08-2010, 08:01 PM
To amplify on Al's remarks: You do not need a double-pole switch to switch between 0 and 1 (if that is your intent): A single pole will do fine.

To wire this, simply connect one side of the switch to ground and the other side to the spike input. Also on the other side connect a 10,000 Ohm resistor (1/8 or 1/4 watt would be fine) to your voltage source (5V if you want to control a spike).

When the switch is closed the spike sees ground (as you would expect). The minimal current flowing through the "pull up" resistor will not affect this. When the switch is opened, the voltage source will appear on the 'spike' side of the switch. This happens because the input resistance (impedance, actually) of the spike is several orders of magnitude greater than 10,000 Ohms.

This is how these things are done. Good luck.

FRC4ME
05-09-2010, 02:53 AM
FRC,
You should do some investigation into pullup resistors. The input circuit of the Spike is a opto isolator so a pullup to 5 volts (or 12) would set the relay in one direction and a short to the common terminal would turn off the opto isolator and set the Spike for the other direction.

To amplify on Al's remarks: You do not need a double-pole switch to switch between 0 and 1 (if that is your intent): A single pole will do fine.

To wire this, simply connect one side of the switch to ground and the other side to the spike input. Also on the other side connect a 10,000 Ohm resistor (1/8 or 1/4 watt would be fine) to your voltage source (5V if you want to control a spike).

When the switch is closed the spike sees ground (as you would expect). The minimal current flowing through the "pull up" resistor will not affect this. When the switch is opened, the voltage source will appear on the 'spike' side of the switch. This happens because the input resistance (impedance, actually) of the spike is several orders of magnitude greater than 10,000 Ohms.

This is how these things are done. Good luck.

Thanks for the info. This makes me think of using the red light sensors - another component we have far too many of - to read "punch cards" of sorts containing the input values. I assume the same pull-up configuration would have no problems working with an NPN transistor triggered by a sensor, right?

DonRotolo
05-09-2010, 08:59 AM
Correct, that should work fine. If not, investigate using a pull-down resistor instead. While this is not considered "good practice", under carefully defined conditions it will be fine.