Diodes and what do they do?

Hello everyone, i am the team 987 leader here in vegas. i was wondering what exaclty is a Diode, and what does it do for us. our mentor was telling us we could use it for more fuctions on one relay. if so that would be great - but how do i hook it up? also, where can i get some diodes? Also, how do i change my profile here on the site? i would like to add a picture. thanks! good luck everyone.

Dave

a diode converts AC current to DC current.

you can by diodes at any electronic store ( assuming they are on the parts list, im not sure if they are restricted or not)

to change your profile click on the profile link right under the chiefdelphi logo on the topleft corner of your screen.

A diode only allows electricity to flow one way through it. How does this help, you may ask? Well, if you remember that relays can either go forward (+ voltage applied to + terminal) or backwards (- voltage to + terminal, + voltage to - terminal), you’ll see some very interesting possibilities. Check out the diagram on the bottom of Page 11 of the Robot Rules. It’s got the wiring info necessary to drive two solenoid valves with just one relay. My advice would be to take some time and see if you can figure out how it works on your own. If you get stuck, I’m sure someone here will be able to help you. Just remember, electricity can only flow in the directiont the arrows are pointing.

*Originally posted by Trashed20 *
a diode converts AC current to DC current.

You are right, but that is sort of a side-effect of diodes. Diodes are semiconductor devices that pass current in one direction only. For example, if you have a 5V battery, current will only pass when you place the more positive terminal to the anode of the diode. Also, current will not pass until the voltage reaches a certain level known as the voltage threshold. The reason that AC is converted to DC is that the lower (negative) voltages won’t pass through the diode, effectively cutting them off. This is the basis for tuning circuits.

The diode that SuperDave was refering to was probably the one used for the double solenoid. That diode blocks current in the circuit that FIRST gave to use one relay for both solenoid valves. I’ll try to find where it is in the manual for you.

*Originally posted by Adam Shapiro *
a diode converts AC current to DC current.

You are right, but that is sort of a side-effect of diodes. Diodes are semiconductor devices that pass current in one direction only. For example, if you have a 5V battery, current will only pass when you place the more positive terminal to the anode of the diode. Also, current will not pass until the voltage reaches a certain level known as the voltage threshold. The reason that AC is converted to DC is that the lower (negative) voltages won’t pass through the diode, effectively cutting them off. This is the basis for tuning circuits.

The diode that SuperDave was refering to was probably the one used for the double solenoid. That diode blocks current in the circuit that FIRST gave to use one relay for both solenoid valves. I’ll try to find where it is in the manual for you. (edited: apparently it’s on page 11…thanks rob :D)

Super Dave,
Diodes are pretty handy devices but in relation to the robot, they can only be used in the custom circuit board or to control the function of pneumatic cylinders through the solenoids as described in an earlier post. They are available from Digikey if you have a minimum order of other stuff, or you can obtain the same part from Radio Shack. You are looking for 1N4000 series diodes. (1N4001, 1N4002, etc.)
Please note that use of the “Blue Spike” allows you to control two solenoids without using diodes.
See this site for details…
http://www.innovationfirst.com/FIRSTRobotics/pdfs/SpikeBLUEUsersManual.pdf

Question about the schematic in the manual of how to use diodes to operate a double action solenoid from one spike… wouldn’t it be possible to use the 12v LED’s given in the kit to do the same thing as those diodes? Or would it be to much resistance?

Another use of diodes with solenoid valves or relays is because of the voltage spikes that appear when you turn off the solenoid valve or relay.

Here is a good description:
](http://www.4qdtec.com/catch.html)

All,
I did forget to mention that diodes are used as spike suppression. They are wired in parallel with the solenoid coil and the cathode (banded end) should be connected to the side of the solenoid connected to the positive terminal of the battery or the plus output of the Spike.
LEDs can be used as diodes except that LEDs have about a 2 volt drop across them as opposed to 0.6 volts drop of the average silicon diode and they cannot handle high currents. When diodes fail they usually short so having a shorted diode across a solenoid would prevent the solenoid from operating.

Dave Allways remember when you see a diode on a schematic it is an arrow pointing to a minus - symbol.Allways connect the minus symbol to ground and current will flow thru it …if connected to + the current will be blocked its all a mattter of how you want to use them… hope this helped…easier than remembering cathode and anode.
Jim :ahh: