3 Weeks Remaining: Small Scale Prototype Wayside, Mechanism and Power Consumption

-
I. ULTRACAPACITORS 
1. Series Balancing
These devices limit the voltage and balance each capacitor. These PCBs can be combined to make a circuit with a combination of series and parallel:
 
2. MOSFET Charging
Using MOSFETs to control the source current. We can quickly charge the UCAP bank within the confines of the maximum current ratings. When the voltage reaches 2.65V, the current will be controlled down to roughly 1A to allow the balancing PCBs to work and to prevent overcharging.  


   a. Measuring Voltage across each UCAP
   The individual monitoring of each UCAP is essential in making sure it does not over charge. Measuring the voltage using an extended analog input such as the Mux Shield II (http://mayhewlabs.com/products/mux-shield-2)The individual monitoring of each UCAP is essential in making sure it does not over charge. Measuring the voltage using an extended analog input such as the Mux Shield II (http://mayhewlabs.com/products/mux-shield-2). 

  b. Measuring UCAP Input Current
   Using a high current sensing device designed to output 0-5V to a micro-controller, we can read the initial and continuous current draw from the solar panels to the UCAPs. YouTube videos on how to do this: 1. https://www.youtube.com/watch?v=UF5jrnXvTlM   2. https://www.youtube.com/watch?v=lisprJs5sNU. 
30A Hall Effect Current sensor: 


  c. Sending PWM signal to charging MOSFET based on current and voltage readings.
     With an initial current read, the micro controller can send a PWM signal to a MOSFET and control the current into the UCAPs which creates a constant current charger. Allowing maximum continuous current into the UCAPs until the voltage exceeds the limit is necessary to charge as fast as possible. This technique will be applied to both UCAP banks.

II. Mechanism CAD
















































We have assumed that the longest part of the mechanism have the least factor of safety (right figure). This could be solved by increasing the thickness of the part, by reducing the overall length or changing material composition.







Revised model might look like this to accomplished better Factor of Safety


III. Force Calculations and  Power Consumption Graph

Comments

Post a Comment

Popular posts from this blog

4 Weeks remaining: Small Scale Prototype

-
Image
Wayside Power Small Scale Prototype:  Update 4 Weeks remaining Issues this week:   Maxwell has still not gotten back to us, so we have begun to look for cheaper alternatives If we create a supercap bank made up with many 2.7V cells in combination of series and parallel, we will be able to save money. This does cause the charging time to increase to about 4 minuets, up from about 45 seconds, as each cell can only handle about 30A of current vs 2000A with the other more expensive modules.   We will have to solder all of these together.  We will have to create a casing to hold and easily assemble, dissemble.  We can use SAB MOSFETS to balance our series stack and prevent overcharging instead of trying to match a mosfet of the shelf with our ucap modules, this is a good thing! These are specifically designed to be a low cost and low power usage solution to balancing supercaps in series. https://www.digikey.my/en/videos/a/advanced-linear-devices/using-mosfets-to-b
Read more