![]() Each water source carries different amounts of these salts which means that their salt concentrations are different as well. Animals and plants need these salts to grow, develop, and stay healthy. It always contains some dissolved mineral salts. Solutions with the same salt concentrations are also called isotonic. No water is moving in this case as the concentrations are already balanced. At this point, the salt concentration inside the potato cells and inside the cup are exactly the same. This should be where your data curve and your start length line intersect. If you made the graph you should have noticed that there is a salt concentration at which the potato strip neither expands nor shrinks. This leads to shrinking of the potato cells which explains why the potato strips get smaller in length and diameter. Once the salt concentration in the cup gets higher than inside the potato cells, water moves out of the potato into the cup. The opposite is the case in the higher concentrated salt solutions. As a result, the whole potato strip gets bigger. The incoming water in the potato cells pushes on the cell walls and makes the cells bigger. To balance out these concentration differences, the water from the cup moves inside the potato cells where there is a higher concentration of salts and less water. The 0 grams saltwater solution is hypotonic compared to the solution inside the potato cells, which means that it contains less salts and more water. Potatoes are made of cells and their cells have cell walls that act as semipermeable membranes. The shrinking and expanding of the potato strips is due to osmosis. (If you didn't see any significant changes after 30 minutes, leave the potato strips in the saltwater solutions longer). Whereas the potato strips in the "0 gram" cup got larger in size, the other potato strips probably got shorter after leaving them in the saltwater for 30 minutes. However, when you put them into the different saltwater solutions this changes. ![]() Throw the potato strips into the compost and clean up your workspace.ĭid you make your potato strips shrink and expand? You should have! At the beginning all the potato strips should have had the same length and should have all felt the same. steps = Amount of Steps to Travel (200 Steps = 1 Rotation given 1.Discard the saltwater solutions in the sink. Recommend attaching a 2 pin jumper cap between EN and GND on the CNC Shield. Used to determine the directions of the motors (clockwise or counterclockwise) Use the provided code below to test if all 3 stepper motors are working properly. HC-05: RX -> TX, TX -> RX, VCC -> 5V, GND -> GNDĮlectromagnet: SIG -> SpnEn, VCC -> 5V, GND -> GND Stepper Motors: 4 wires from the stepper driver to the 4 pins located by the stepper driver. (Must increase number of steps in code sample if FULL step is not desired).Ĭonnect the following devices using the wiring below: Optional: Install jumper caps to enable micro stepping. Run a sample test program to determine if the stepper motors are connected properly and functioning. Once again, refer to the data sheet as many manufacturers may have changed the wiring for your stepper motors. Once the drivers are connected and set, connect the stepper motor cables to the 4 pins allocated. Refer to the data sheets for your motors to ensure you do not over-power or under-power the stepper motors. The current_limit is determined by the stepper motor specifications. This formula is different for various drivers, please check your driver's specifications before continuing as too much current will melt the coils and insufficient current will prevent the motor from moving. The formula to solve for VREF on a DRV8825 is voltage_read * 2 = current_limit. Once all stepper drivers are connected, connect the power supply terminals to the power terminal blocks on the CNC shield and set the VREF values appropriately. Ensure the enable pin on the stepper driver aligns with the enable pin on the CNC shield. ![]() Be sure to add the heatsinks to the stepper drivers prior to attaching to the CNC shield. Insert the 3 DRV8825 stepper drivers into the X, Y, and Z labeled sections (Section A remains empty). After gathering all the materials and tools, start by fixing the CNC shield upon the Arduino. ![]()
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