I am trying to make a machine that will test bicycle brakes to determine the ratio of front/rear stopping power. I am going to put the front and rear wheel on independent cement rollers, and determine the power dissipated by their deceleration.
Project requirements:
-read speed of each roller (hall effect sensor?)
-control 2 motors that speed up the wheels to the same speed, then shut them off
-actuate a solenoid or air piston to apply braking force
-record data in some way that I can then graph the speeds of each roller vs. time on the same graph.
-repeat process
This whole thing seems basic enough but I have very little experience with the controls portion. Building the thing will not be a problem. Any and all help will be greatly appreciated. I am looking forward to learning about the arduino and what it can do.
Thank you very much for your reply. I am looking to use two 1/4 - 1/2 hp motors. How would I determine which motors and controllers are easier for the arduino to control?
My idea is to write data to a memory card or usb stick, and from there, plug it into excel or matlab for the graphs and data analysis.
The rollers definitely have enough energy in them to use a relay. I'm new to this vocabulary so to clarify, you're saying I could use two 1/4- 1/2 hp motor that runs off of a 120v single phase wall outlet and control that using a relay that is controlled by the arduino?
Forgive my huge lack of knowledge on this subject. I know I sound stupid but I really appreciate the help.
I have just simplified the project: I will use one motor that is connected to both rollers, via freewheels on each roller. This way, the arduino only needs to control 1 motor, and it can speed up to a certain speed, then simply click the ss relay off, not needing to keep the rollers at a constant speed. The rollers then spin down independently.
If you wanted to save cost, you could use a 20 amp "plenty big" light switch to control the motor and use the Arduino to watch the switch to see when you turn it off.
You may also want to implement something to measure your braking pressure on the brake pads.
This is what I have come up with so far. I'll be using the arduino to control 3 solid state relays that run 110 VAC. Two SSRs will control air solenoid valves. One to activate the piston, and another to bleed off pressure when it is deactivated. The third SSR will control the motor. I am going to use 2 hall effect sensors or reed switches to read the speed of each roller. When the motor starts, the rollers will speed up. When the hall effect sensors read a certain speed, the motor will turn off, and one of the solenoid air valves will open, applying the brake. At this time, data will also be recorded and sent to a computer. The brake will remain on until a roller slows to a certain speed. Then, the two solenoid valves will switch, releasing pressure on the piston. The motor will start again, thus repeating the process. I hope to be able to let the machine run for a while, and be able to come back and graph the roller speed data in excel or matlab.
I have ordered these relays to drive a 120v AC motor and solenoid valve:
I was trying to find out if I can power the relays from the arduino directly or if I need some extra circuitry. I'm new to reading electrical diagrams but this is what I found for a DC relay (my relays control AC):
Since the relays I have bought go down to 3v, I should be able to power it from the arduino's 5v, however I am worried that the relay may require more current than the arduino can put out. Any tips/hints? My thoughts are to use a separate 5v power supply from an old cell phone charger to isolate the arduino, but not sure how, or if even necessary.
As already stated you can drive a SSR directly from an arduino digital output pin.
Other things to be aware of when using SSR.
Be careful of how much current you try and use. That 25amp current rating will only hold if you provide a very large heatsink using proper mounting paste, etc. So when first testing out a application be sure to check how hot the SSR is getting and take measures necessary.
Second point is most SSR don't deal well with large inductive loads like motors and solenoids. This can result in unreliable turning on and off of the load. If you experience such flaky switching then do a search and research on the term "Snubber Circuit".
