POM PPM Parking Meter
I found this parking meter at Princess Auto yesterday. Made by POM Inc., this meter is called the PPM.
I got it to work by adding a rubber band with just enough tension to depress the turn-detect lever when the lever is turned. The meter has knobs where a tensioned spring was attached. I’ll have to find a decent spring somewhere.
Opening it up, I found that the coin detector uses a series of armatures and four switches to detect which coin was inserted.
Upon examination, it has 6 buttons:
- (Top Left) Yellow button for debug output
- (Bottom Left) Yellow button for turn-sense
- White buttons (4) for coin sense
When a Quarter is inserted into the proper slot and the arm is turned…
- As the coin lever is turned, the turn button is pressed.
- As it passes the buttons, the quarter makes the arm hit all 4 white buttons, in a clockwise order starting with the top left.
- When the turn lever is released, it returns to its original position, and releases the turn button.
When a Dime is inserted into the proper slot and the arm is turned…
- As the coin lever is turned, the turn button is pressed.
- As it passes the buttons in a clockwise order starting with the top left, the quarter makes the arm skip the first white button, and hits the remaining 3 white buttons.
- When the turn lever is released, it returns to its original position, and releases the turn button.
When a Nickel is inserted into the proper slot and the arm is turned…
- As the coin lever is turned, the turn button is pressed.
- As it passes the buttons in a clockwise order starting with the top left, the quarter makes the arm skip the first 2 white buttons, and hits the remaining 2 white buttons.
- When the turn lever is released, it returns to its original position, and releases the turn button.
When you press the Debug button, the front LCD shows the following:
- Test pattern: “c2:2c”, where the last ‘c’ is backwards.
- Firmware Version?: “0159”, also the number writen on a sticker on top of the ST27C256
- Parking Limit: “0002”, maximum number of hours allowed to park
- Route?: “0321”, also printed on a sticker on the back of the meter. This was the same for other meters i saw.
- Unknown: “8:5”, “8:6”
Interesting innards:
LCD/LEDs
- LCD1: LCD, Front: 4-digit, “88:88” LCD
- LCD, Back: Red, Clear background. No text.
- D3: Red LED, (clear casing)
- D4: IR LED
- D5: IR Sensor
Switches
- SW5,6: Yellow Switches (Surface mount)
- SW1,2,3,4: White Switches (Surface mount)
ICs
- U6: Motorola MC14519B – Four bit AND/OR selector
- U2: Motorola MC14521B –
- U7: Motorola MC145453FN – LCD 33-Segment LCD Driver, Serial, CMOS
- U5: Motorola MC68HC11A1FN – Motorola 8-bit Microcontroller, 256 Kbit RAM, A/D converter, EEPROM
- U4: Fairchild MM74HC373WM
– 3-STATE Octal D-Type Latch
- U3: THMOS ST27C256 – 256Kbit (32Kx8) CMOS 3-STATE (UV-Erasable?) EPROM
- U1: 271BC – Programmable Low-Power OP-Amp
- U8: Motorola HC20 – Dual 4-input NAND gate
- U9: 74HC02M – Quad 2-Input NOR Gate
Headers
- J2: 4-pin header
- JP4, JP3, JP2, JP1: Jumpers, unpopulated, to ground certain pins on U5
See also:
http://www.globalnerdy.com/2008/07/17/rubyfringe-guide-active-surplus-aka-hardware-nerdvana/
Pics in action:
http://www.sonomatlc.org/Parking/PBDs/Pkg_Benefit_Districts.htm
http://www.dkimages.com/discover/DKIMAGES/Discover/Home/Geography/North-America/United-States/Travellers-Needs/Practical-Information/Transportation/Roads/Chicago/Parking-Meter/Parking-Meter-1.html