Water Task

User avatar
PM2017
Member
Member
Posts: 524
Joined: January 20th, 2017, 5:02 pm
Division: Grad
State: CA
Has thanked: 23 times
Been thanked: 13 times

Re: Water Task

Post by PM2017 »

mpnobivucyxtz wrote:How are you all amplifying the current needed for the circuit to do anything functional? When I add water to my concentration of salt, it transmits nowhere near enough to power any of my other tasks. I looked into transistors and op-amps but using them looks so complicated :?
Mine is actually connected to a relay, so it doesn't take that much voltage current. Also, if you must increase the current, put the electrodes (or whatever the disconnected wires are) closer together, as well as increasing the amount of salt. maybe, if you are using another resistor in the same branch of the circuit and if you can get the resistance across the saline water to be consistent between runs, maybe calculate that into your circuit, and not add as much extra resistance. (i.e. if the specs ask for a 560 ohm resistor, and the water has a resistance of 500 ohms, only use a 60 ohm resistor. <--- This is assuming series. I don't know how you would use parallel. Also, these values are just something I pulled out of thin air, so you should do the actual testing before subtracting 500 ohms from your circuit.)

EDIT: First sentence initially said voltage, instead of current.
West High '19
UC Berkeley '23

Go Bears!
mpnobivucyxtz
Member
Member
Posts: 34
Joined: January 22nd, 2018, 6:25 pm
Division: C
State: NY
Has thanked: 0
Been thanked: 0

Re: Water Task

Post by mpnobivucyxtz »

PM2017 wrote:
mpnobivucyxtz wrote:How are you all amplifying the current needed for the circuit to do anything functional? When I add water to my concentration of salt, it transmits nowhere near enough to power any of my other tasks. I looked into transistors and op-amps but using them looks so complicated :?
Mine is actually connected to a relay, so it doesn't take that much voltage current. Also, if you must increase the current, put the electrodes (or whatever the disconnected wires are) closer together, as well as increasing the amount of salt. maybe, if you are using another resistor in the same branch of the circuit and if you can get the resistance across the saline water to be consistent between runs, maybe calculate that into your circuit, and not add as much extra resistance. (i.e. if the specs ask for a 560 ohm resistor, and the water has a resistance of 500 ohms, only use a 60 ohm resistor. <--- This is assuming series. I don't know how you would use parallel. Also, these values are just something I pulled out of thin air, so you should do the actual testing before subtracting 500 ohms from your circuit.)

EDIT: First sentence initially said voltage, instead of current.
This is really helpful, thank you so much!! Are you using a 5v relay? I have one that came with my Arduino but I don't know whether it'll pick up the current.
User avatar
PM2017
Member
Member
Posts: 524
Joined: January 20th, 2017, 5:02 pm
Division: Grad
State: CA
Has thanked: 23 times
Been thanked: 13 times

Re: Water Task

Post by PM2017 »

mpnobivucyxtz wrote:
PM2017 wrote:
mpnobivucyxtz wrote:How are you all amplifying the current needed for the circuit to do anything functional? When I add water to my concentration of salt, it transmits nowhere near enough to power any of my other tasks. I looked into transistors and op-amps but using them looks so complicated :?
Mine is actually connected to a relay, so it doesn't take that much voltage current. Also, if you must increase the current, put the electrodes (or whatever the disconnected wires are) closer together, as well as increasing the amount of salt. maybe, if you are using another resistor in the same branch of the circuit and if you can get the resistance across the saline water to be consistent between runs, maybe calculate that into your circuit, and not add as much extra resistance. (i.e. if the specs ask for a 560 ohm resistor, and the water has a resistance of 500 ohms, only use a 60 ohm resistor. <--- This is assuming series. I don't know how you would use parallel. Also, these values are just something I pulled out of thin air, so you should do the actual testing before subtracting 500 ohms from your circuit.)

EDIT: First sentence initially said voltage, instead of current.
This is really helpful, thank you so much!! Are you using a 5v relay? I have one that came with my Arduino but I don't know whether it'll pick up the current.
Yes, I'm using a 5V relay.
West High '19
UC Berkeley '23

Go Bears!
antigem
Member
Member
Posts: 7
Joined: December 5th, 2017, 3:00 pm
Division: C
State: WA
Has thanked: 0
Been thanked: 0

Re: Water Task

Post by antigem »

Would having water in an already closed container count? I was going to fill a plastic test tube or graduated cylinder a quarter full with water, put my wires in so that they aren't touching the water. Then I would cap it off with hot glue and put the entire thing on a pivot so that when the test tube would tip over, the water would rush to the other side and complete the circuit. But i'm worried cause the rules say that you have to add water to a closed container, and nothing about already having water in it.
Central Valley High School, WA

2019 events and place at regionals:
Boomilever 4th
Write it Do it 2nd
Mission Possible 2nd
Thermodynamics 2nd
jinhusong
Member
Member
Posts: 171
Joined: March 16th, 2017, 3:34 pm
Division: C
State: CA
Has thanked: 2 times
Been thanked: 2 times

Re: Water Task

Post by jinhusong »

antigem wrote:Would having water in an already closed container count? I was going to fill a plastic test tube or graduated cylinder a quarter full with water, put my wires in so that they aren't touching the water. Then I would cap it off with hot glue and put the entire thing on a pivot so that when the test tube would tip over, the water would rush to the other side and complete the circuit. But i'm worried cause the rules say that you have to add water to a closed container, and nothing about already having water in it.
When I was watching one of the invitations, the ES said it is NOT OK. The students argued what if the container is like the shape of sand-clock. The ES said that will be OK. Then the student said, what's the difference, still one container just narrow in the middle. Still, the ES did not buy it.
nicholasmaurer
Coach
Coach
Posts: 422
Joined: May 19th, 2017, 10:55 am
Division: Grad
State: OH
Has thanked: 1 time
Been thanked: 22 times

Re: Water Task

Post by nicholasmaurer »

antigem wrote:Would having water in an already closed container count? I was going to fill a plastic test tube or graduated cylinder a quarter full with water, put my wires in so that they aren't touching the water. Then I would cap it off with hot glue and put the entire thing on a pivot so that when the test tube would tip over, the water would rush to the other side and complete the circuit. But i'm worried cause the rules say that you have to add water to a closed container, and nothing about already having water in it.
The task is clearly defined as adding water to a container, which is not what you describe.
Assistant Coach and Alumnus ('14) - Solon High School Science Olympiad
Tournament Director - Northeast Ohio Regional Tournament
Tournament Director - Solon High School Science Olympiad Invitational

Opinions expressed on this site are not official; the only place for official rules changes and FAQs is soinc.org.
Locked

Return to “Mission Possible C”

Who is online

Users browsing this forum: No registered users and 2 guests