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...

  1. As the coin lever is turned, the turn button is pressed.
  2. As it passes the buttons, the quarter makes the arm hit all 4 white buttons, in a clockwise order starting with the top left.
  3. 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...

  1. As the coin lever is turned, the turn button is pressed.
  2. 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.
  3. 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...

  1. As the coin lever is turned, the turn button is pressed.
  2. 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.
  3. 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:

  1. Test pattern: "c2:2c", where the last 'c' is backwards.
  2. Firmware Version?: "0159", also the number writen on a sticker on top of the ST27C256
  3. Parking Limit: "0002", maximum number of hours allowed to park
  4. Route?: "0321", also printed on a sticker on the back of the meter. This was the same for other meters i saw.
  5. 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

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reprogramming the timer

Hey guys, I've never worked with one of these before, however I picked one up from active last year some time, in hopes that it would inspire eventually, and IT DID!!!

however I had to re-program the timer, because the time was adding up too fast.

I managed to spend a few hours today pluckin around with the program settings hidden in the debugger and managed to re-program the timer values to my own settings!

if anyone needs help performing this task on the same POM PPM model, email me and I can do my best to explain what I did.

I saw the same parking

I saw the same parking meter but I didn't think all of the coin selector hardware was there. I guess it was just simpler than I expected. Is there anything to prevent someone from inserting a washer or slug?

POM PPM

No, there isn't, and it's probably one of the reasons it was discontinued for meters with less mechanical methods. Essentially any coin/object that is close in size to an actual coin would trigger the right buttons.

Unfortunately, I sent an email to POM inquiring about service manuals for the PPM since their website offers newer service manuals online, and for the older ones says to "Contact Us". They simply said to "contact the city I worked for". I replied that I didn't work for the city, but the meters were appearing in surplus stores across the country. I didn't hear back from them, so I assume they are unwilling to help.

Can anyone dig up an old service manual for one of these?

Does anyone have a way to dump data from a Motorola MC68HC11A1FN? I know that current parking meters have a handheld meter-reader that downloads information from the meter via the IR Sensor and IR LED... That might be interesting to decode.

I've got some internal shots of the circuit board that I've been meaning to post, there just aren't enough hours in the day.

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