Published December 30, 2015 © MIT

EV Charger

EV chargers are starting to show up everywhere. Why not at your place?

AdvancedFull instructions provided1,711

Things used in this project

Hardware components

Futaba VFD Display

Magtek Swipe Reader

Patlite Signal Tower

Solid State Relay

contactor

PC Power Supply

Hand tools and fabrication machines

Soldering iron (generic)

Story

EV chargers are starting to show up everywhere. We had started an EV project at school and we considered to big commercial chargers but what about the DIIY'er? We made this simpler charger. The software interfaced with our card sytem so any community member could activate the charger with their ID card. Instead of an SAE cord we used a standard NEMA electrical outlet just like at the RV parks or Boat docks.

Step 1: Small Prototype and Proof of Concept Charger

1 / 7

The first thing to do is build the prototype. Its a small version of the charger that can sit on your desktop. Great for testing code updates too.

I used some surplus Magtek serial readers I had lying around. The came from old Gas Pumps and had a small regulator board attached. I replaced that board with a new one holding a small pic that could watch the serial stream to the display and intercept some control characters. I chose characters the display would ignore but that could be used to control the signal lights and charger port relay.

They have a standard RS232 serial interface. I made a small plate from a scrap of aluminum to hold 4 led's and mounted it to the face of the reader.

3 of the led's are for status of the system and the 4th is to show when the charger port is on. We used Patlite Signal Tower's in the final units. You commonly see these in the supermarket and the checkout line to tell you which register is open.

A green light means the charger is ready and available. A yellow light means the charger is in use. And a red light means there is some fault in the system. Loss of power, network or some other reason the machine is unavailable.

Step 2: Hardware

To get the Linkit to communicate with the display and readers all you need is an RS-232 level shifter. I used the ubiquitous Max232 and mounted it to a proto shield board.

There is plenty of space here to place the pic micro I added to the Magtek reader board. You could even change the code to use Linkit One Digital I/O pins to drive the lights and SSR directly. You would only need a small transistor array chip like a ULN2003. This would eliminate the need for the PIC altogether but I like having the drivers isolated to a separate part of the enclosure. This keeps HV away from the Linkit One.

Step 3: The Larger Deployment Model

1 / 6

This one used the real full sized components arranged on a large piece of particle board and covered by Plexiglas. We had this on display for green week and encouraged people to swipe their cards to see their name appear on the display. Thinking back we should have used the log to give away prizes....

Step 4: Circuitry

1 / 2

It's all pretty straight forward. The Patlite was driven by some darlington transistors. I didnt include detailed schematics since if you are into EV's you should be able to wire a darlington driver blindfolded. As you can see I made my darlington drivers from discrete components but with the new LED Patlite's I found KSP-13's work great.

The unit was powered by a standard open frame power supply most often used in external 5.25 PC Hard Drive cases.

We used a solid state relay to provide a 120V feed to power a large 3 phase contactor.

Even though we know most people used 5-20 and 6-20 outlets on their homebrewed EV's we thought it might be more useful if we also added L14-30 and L21-30 outlets for the bigger projects. I even took a trip to some local stores that supply RV's so see what kinds on power adapter cables they usually stock.

Step 5: Software

1 / 2

We used a proprietary card system vendor that charged us $5000 for the license to interface to their backend. Probably the most expensive part of the whole project. I really wanted an open alternative.This was easily made using just the power of the Linkit One.

I've attached a demo sketch to get you started and allow you to test a prototype quickly. There is a live sketch with no checks for card number. This way any card would work.

The SMS capabilities of the Linkit can be used to send text notifications when the time runs out. I put the VFD message in and then realized it wasnt really needed. This would be a nice improvement over our email only notifications but without the fancy notifications it can be relatively cheap to operate. This way we can run these without having to charge any money. I thought about using the Paypal api but I want this to be a free community resource.

The DIY EV community has a list of local places you can charge your car. Id love to see these on the walls of garages in the community.

Step 6: Testing

Here are a few movies of it in action.

Code

//****************************************************************
//*  Name    : EV Charger Demo                                   *
//*  Author  : Robert Joseph Korn                                *
//*  Notice  : Copyright (c) 2015 Open Valley Consulting Corp    *
//*  Date    : 12/14/15                                          *
//*  Version : 1.1                                               *
//*          :                                                   *
//*  Notes   :  Charger Control Codes                            *
//*          :  03 - Charger On                                  *
//*          :  04 - Charger Off                                 *
//*          :  07 - Initialize Display                          *
//*          :  12 - Clear Display(must be followed by cr lf)    *
//*          :  22 - Signal Tower Off                            *
//*          :  23 - Signal Tower Red                            *
//*          :  24 - Signal Tower Yellow                         *
//*          :  25 - Signal Tower Green                          *
//*          :                                                   *
//*          :  States                                           *
//*          :  0 - Waiting for Swipe                            *
//*          :  1 - Parsing Track 1                              *
//*          :  2 - Parsing Track 2                              *
//*          :  3 - Processing Swipe                             *
//*          :                                                   *
//*          :                                                   *
//****************************************************************

int SER = 0;
int state = 0;
int numlen=0;
int namlen=0;
int o=0;
char nam[255];
char num[55];

void setup() {

  Serial1.begin(9600);
  Serial1.write(22); 
  Serial1.write(4);
  Serial1.write(12); 
  Serial1.println();
  Serial1.write(12);
  Serial1.println("MediaTek Linkit One");
  Serial1.write(14);
  Serial1.println("  EV Charger Demo  ");
  delay(2500);   
  Serial1.write(25);
  Serial1.write(12);
  Serial1.println("EV Charger is Ready");
  Serial1.write(14);
  Serial1.println("Swipe Card to Begin");

}

void loop() {
   
          if( state == 3 ) 
          {     
              Serial1.write(24);
              Serial1.write(12);
              Serial1.println("      Welcome       ");
              Serial1.write(14);
              
            for(int o=0;o<namlen-1;o++)
             {
               Serial1.print(char(nam[o]));             
             }
             
             Serial1.println("");
             
             delay(2500);   
             Serial1.write(3);
             Serial1.write(12);
             Serial1.println("Charging in Progress");
             Serial1.write(14);
             Serial1.println("  2.0 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  1.9 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  1.8 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  1.7 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  1.6 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  1.5 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  1.4 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  1.3 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  1.2 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  1.1 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  1.0 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  0.9 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  0.8 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  0.7 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  0.6 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  0.5 Hours Remain");

            delay(1000);   
             Serial1.write(14);
             Serial1.println("  0.4 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  0.3 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  0.2 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  0.1 Hours Remain");

             delay(1000);   
             Serial1.write(14);
             Serial1.println("  0.0 Hours Remain");

             delay(1000);   
             Serial1.write(4);
             Serial1.write(12);
             Serial1.println("Charge Time Complete");
             Serial1.write(14);
             Serial1.println(" Notification Sent");

             delay(2500);   
             Serial1.write(25);
             Serial1.write(12);
             Serial1.println("EV Charger is Ready");
             Serial1.write(14);
             Serial1.println("Swipe Card to Begin");

            numlen=0;
            namlen=0;
            state=0;     
          }
  
  if (Serial1.available() > 0) {
      SER = Serial1.read(); 

  switch(state)
  {
    case 0:if (SER==0x3B)  
               {
                 state=1;
               }
           if (SER==0x25)  
               {
                 state=2;
               }break;
               
    case 1:num[numlen]=SER;  
            numlen++;             
              if (SER==0x3F)  
               {
                 state=3;
               }break;
               
    case 2:nam[namlen]=SER;  
            namlen++;              
              if (SER==0x3F)  
               {
                 state=0;
               }break;
          
     default:break;
  }
 
  }

}

//****************************************************************
//*  Name    : Serial Demo                                       *
//*  Author  : Robert Joseph Korn                                *
//*  Date    : 12/14/15                                          *
//*  Version : 1.1                                               *
//*  Notes   : Really just the software serial demo              *
//*          : changed for serial1                               *
//****************************************************************

void setup() {
  Serial.begin(9600);
  while (!Serial) {
    ; // wait for serial port to connect. Needed for native USB port only
  }

 Serial1.begin(9600);
}

void loop() { 
  if (Serial1.available()) {
    Serial.write(Serial1.read());
  }
  if (Serial.available()) {
    Serial1.write(Serial.read());
  }
}

'****************************************************************
'*  Name    : EV-Charger-SERIAL.BAS                                 *
'*  Author  : Robert Joseph Korn                                *
'*  Notice  : Copyright (c) 2015 Open Valley Consulting Corp    *
'*  Date    : 12/15/2015                                         *
'*  Version : 1.0                                               *
'*  Notes   :                                                   *
'*          :                                                   *
'****************************************************************
  
DEFINE  OSC     10
 
DEFINE HSER_RCSTA 90h 
DEFINE HSER_TXSTA 20h            
DEFINE HSER_BAUD 9600 
DEFINE HSER_CLROERR 1

x       var     word

        ADCON1 = $7f 

char    var     BYTE

red     VAR     PORTB.7
yellow  VAR     PORTB.6
green   VAR     PORTB.5
charge  VAR     PORTA.0
        
        PORTB = 0
        TRISB = $7e

        low charge
        low red
        low yellow
        low green
        
        on interrupt goto serial
 
        INTCON = %11000000
        PIE1 = %00100000
 
         goto    main


' interrupt service routine        
        disable
serial:
       
        hserin 0, endisr, [char]
        
        if  char = $04 then 
            low charge
        endif
       
        if  char = $03 then 
            high charge
        endif
         
        if  char = $16 then 
            low red
            low yellow
            low green
        endif
        
        if  char = $17 then 
            high red
            low yellow
            low green
        endif
        
        if  char = $18 then 
            low red
            high yellow
            low green
        endif
        
        if  char = $19 then 
            low red
            low yellow
            high green
        endif

endisr:
        resume
        enable
        ' end of ISR
       
main:     
       pause 500
       goto main

//****************************************************************
//*  Name    : EV Charger Live                                   *
//*  Author  : Robert Joseph Korn                                *
//*  Notice  : Copyright (c) 2015 Open Valley Consulting Corp    *
//*  Date    : 12/14/15                                          *
//*  Version : 1.1                                               *
//*          :                                                   *
//*  Notes   :  Charger Control Codes                            *
//*          :  03 - Charger On                                  *
//*          :  04 - Charger Off                                 *
//*          :  07 - Initialize Display                          *
//*          :  12 - Clear Display(must be followed by cr lf)    *
//*          :  22 - Signal Tower Off                            *
//*          :  23 - Signal Tower Red                            *
//*          :  24 - Signal Tower Yellow                         *
//*          :  25 - Signal Tower Green                          *
//*          :                                                   *
//*          :  States                                           *
//*          :  0 - Waiting for Swipe                            *
//*          :  1 - Parsing Track 1                              *
//*          :  2 - Parsing Track 2                              *
//*          :  3 - Processing Swipe                             *
//*          :                                                   *
//*          :                                                   *
//****************************************************************

int SER = 0;
int state = 0;
int numlen=0;
int namlen=0;
int o=0;
char nam[255];
char num[55];

void setup() {

  Serial1.begin(9600);
  Serial1.write(22); 
  Serial1.write(4);
  Serial1.write(12); 
  Serial1.println();
  Serial1.write(12);
  Serial1.println("MediaTek Linkit One");
  Serial1.write(14);
  Serial1.println("  EV Charger Demo  ");
  delay(2500);   
  Serial1.write(25);
  Serial1.write(12);
  Serial1.println("EV Charger is Ready");
  Serial1.write(14);
  Serial1.println("Swipe Card to Begin");

}

void loop() {
   
          if( state == 3 ) 
          {     
              Serial1.write(24);
              Serial1.write(12);
              Serial1.println("      Welcome       ");
              Serial1.write(14);
              
            for(int o=0;o<namlen-1;o++)
             {
               Serial1.print(char(nam[o]));             
             }
             
             Serial1.println("");
             
             delay(2500);   
             Serial1.write(3);
             Serial1.write(12);
             Serial1.println("Charging in Progress");
             Serial1.write(14);
             Serial1.println("  2.0 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  1.9 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  1.8 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  1.7 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  1.6 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  1.5 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  1.4 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  1.3 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  1.2 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  1.1 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  1.0 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  0.9 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  0.8 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  0.7 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  0.6 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  0.5 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  0.4 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  0.3 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  0.2 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  0.1 Hours Remain");

             delay(360000);   
             Serial1.write(14);
             Serial1.println("  0.0 Hours Remain");

             delay(1000);   
             Serial1.write(4);
             Serial1.write(12);
             Serial1.println("Charge Time Complete");
             Serial1.write(14);
             Serial1.println("EV Charger is Ready");

             delay(2500);   
             Serial1.write(25);
             Serial1.write(12);
             Serial1.println("EV Charger is Ready");
             Serial1.write(14);
             Serial1.println("Swipe Card to Begin");

            numlen=0;
            namlen=0;
            state=0;     
          }
  
  if (Serial1.available() > 0) {
      SER = Serial1.read(); 

  switch(state)
  {
    case 0:if (SER==0x3B)  
               {
                 state=1;
               }
           if (SER==0x25)  
               {
                 state=2;
               }break;
               
    case 1:num[numlen]=SER;  
            numlen++;             
              if (SER==0x3F)  
               {
                 state=3;
               }break;
               
    case 2:nam[namlen]=SER;  
            namlen++;              
              if (SER==0x3F)  
               {
                 state=0;
               }break;
          
     default:break;
  }
 
  }

}

Credits

Robert Korn

15 projects • 27 followers

I Made the Internet of Things before people had a name for it.

EV Charger

Things used in this project

Hardware components

Hand tools and fabrication machines

Story

Step 1: Small Prototype and Proof of Concept Charger

Step 2: Hardware

Step 3: The Larger Deployment Model

Step 4: Circuitry

Step 5: Software

Step 6: Testing

Schematics

Schematic

Code

EV_Charger_demo.ino

Serial_Test.ino

ev-charger-light-control.pbp

EV_Charger_Live.ino

Credits

Robert Korn

Comments

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EV Charger

EV Charger

Things used in this project

Hardware components

Hand tools and fabrication machines

Story

Step 1: Small Prototype and Proof of Concept Charger

Step 2: Hardware

Step 3: The Larger Deployment Model

Step 4: Circuitry

Step 5: Software

Step 6: Testing

Schematics

Schematic

Code

EV_Charger_demo.ino

Serial_Test.ino

ev-charger-light-control.pbp

EV_Charger_Live.ino

Credits

Robert Korn

Comments

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