Help! Connecting CRIO to the Power Block

[RyanJK]

Hey everyone! So, this year the torch has been passed to me to be the electrical dude. Last year we had someone who actually was studying electrical engineering, but I have no clue and I'm in over my head. I've been able to wire the battery to the power distribution block through the circuit breaker, but now I'm trying to connect the cRIO to the block. I've read in the manual that I need to use 22-14AWG wire. I really don't know what that is, and looking through the inventory list, I don't think any came in the kit of parts.

Also, I know how to use a volt meter to check voltage, but I was wondering if anyone can describe to me how to use the voltmeter to check if the right amount of amperage (40A, 30A, etc.) is coming out of each spot on the power block.

Thanks everyone! I'm the one who knows the most about wiring in the team, but that isn't saying much. We have a mentor coming in a couple days, and he's gonna teach me what I need to know, but he asked me to do this before he came... :ahh:

[Russ Beavis]

http://www2.usfirst.org/ftpdoc/coordination/

Check out the above information from the Robot Quick Build Session. There is a LOT of great info on this FTP server.

Before turning on the power, you'll definitely want to have your mentor check out your wiring job.

Regarding wire size, I use the following link very often to compare gauge (related to wire diameter) versus resistance and current handling capacity. Larger diameter = less resistance and more current capacity.

http://www.powerstream.com/Wire_Size.htm

Russ

[EricVanWyk]

Hey everyone! So, this year the torch has been passed to me to be the electrical dude. Last year we had someone who actually was studying electrical engineering, but I have no clue and I'm in over my head.

Bah, you'll be fine. You are asking the right questions and reading the manual. You'll be teaching others before you know it.

I've read in the manual that I need to use 22-14AWG wire. I really don't know what that is, and looking through the inventory list, I don't think any came in the kit of parts.

AWG stands for American Wire Gauge (http://en.wikipedia.org/wiki/American_wire_gauge). 22-14AWG means between 0.644mm and 1.628mm, if you look at the chart that is about half way down that link.


Also, I know how to use a volt meter to check voltage, but I was wondering if anyone can describe to me how to use the voltmeter to check if the right amount of amperage (40A, 30A, etc.) is coming out of each spot on the power block.

It isn't a good idea to use a multimeter to check for currents in that range - you are likely to damage it. Basically, your meter will draw as much current as is possible. You then need to hope that the circuit breaker blows before the meter or the wires do. You will have to rely on the labels on the circuit breakers.

Always figure out what will limit the current before you measure it. For example, the 5V/6V supply that is featured on the PD, DSC and Analog Breakout has a very good fast acting current limit that will cap instantaneous current to 5 Amps. My multimeters are typically fused at 20A, so they can measure there. Check twice!

[cabbagekid2]

Hey everyone! So, this year the torch has been passed to me to be the electrical dude. Last year we had someone who actually was studying electrical engineering, but I have no clue and I'm in over my head. I've been able to wire the battery to the power distribution block through the circuit breaker, but now I'm trying to connect the cRIO to the block. I've read in the manual that I need to use 22-14AWG wire. I really don't know what that is, and looking through the inventory list, I don't think any came in the kit of parts.

Also, I know how to use a volt meter to check voltage, but I was wondering if anyone can describe to me how to use the voltmeter to check if the right amount of amperage (40A, 30A, etc.) is coming out of each spot on the power block.

Thanks everyone! I'm the one who knows the most about wiring in the team, but that isn't saying much. We have a mentor coming in a couple days, and he's gonna teach me what I need to know, but he asked me to do this before he came... :ahh:

Seems like you think that if you plug the meter into a slot with a 40A breaker it will show 40A on the meter. This is not correct. When you use a meter to measure current, it will tell you the current flowing through at that moment (the amount of current needed to power the device).

You can use it to measure current for smaller devices. But like Eric said I do not recommend using one of those probe meters to measure the current going through a motor (sometimes up to 40Amps). Meters aren't able to handle that.

For motors and high current devices, what we use is a meter that clamps around a cable to check the current flowing through it (rather than the one with just probes).

To measure current with a meter with probes:
1) Plug the black probe into COM (common)
2) Plug the red probe into the ADC port (might say like 10ADC)
3) Turn the dial to point to the indicator for dc current (DCA or maybe A with a solid line over it)
4) Wire the meter in SERIES with what you would like to measure the current for. Voltage is measured in parallel, current in series.