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308 Speedo Repair/Rebuild

Discussion in '308/328' started by alhbln, Aug 22, 2013.

  1. alhbln

    alhbln Formula 3
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    Good news for everyone who needs a Speedo Type 1 repair or conversion but does not care for a DIY approach. I'm happy to announce that Palo Alto Speedometers now offers repairs and conversions based on the circuit board described above :)
     
  2. alhbln

    alhbln Formula 3
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    #152 alhbln, Nov 24, 2014
    Last edited by a moderator: Sep 7, 2017
    A bit of progress, did the hardware design for the new type 2 and 3 board. See below for a first draft of the type 2 shaped circuit board. I've added a small switch for selecting the speedo type (km/h or mp/h). The circuit will be the same for the type 3 board.

    The original type 2 and 3 board design is interesting, my original assumption that there would be two motors (speedo, ODO) was wrong. Instead there is only one motor (driving both the speedo and ODO) and a hall sensor to manage the motor speed by comparing the incoming speedo and motor pulses. This saved time in the production as no final calibration was required anymore, and the hardware for the km/h and mp/h Speedos was nearly identical.
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  3. ZOOOOMZ

    ZOOOOMZ Karting

    Aug 14, 2013
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    Adrian, wow, looks like great progress! If your illustration is meant to be a unified design for both Type 2 and Type 3, a second hole is required in the board, to accommodate a positioning boss molded into the plastic board support. The location and size were in the mechanical dimensions I posted previously.
    Love that you've arrived at a single design that requires no extra calibrations, and just a switch to select km or miles.
    Thanks again for your work, on behalf of all of us who will benefit when our speedos become ill...
     
  4. johnhunt

    johnhunt Formula Junior

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  5. alhbln

    alhbln Formula 3
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    #155 alhbln, Nov 27, 2014
    Last edited by a moderator: Sep 7, 2017
    Not a unified board design yet, but i like your idea with the two different screw holes to accommodate both Speedos. Will make things a bit easier having to produce just one board for both type 2 and 3 speedos in mph and kmh.

    Have done a first design of a replacement PCB with a hall sensor for the later senders, which can be potted in using the original housing (see below). No idea yet about a full replacement of the early senders due to the mechanical requirements yet, hmmm.
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  6. alhbln

    alhbln Formula 3
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    #156 alhbln, Dec 18, 2014
    Last edited by a moderator: Sep 7, 2017
    Assembled the first circuit board for type 2 and 3 speedos. I implemented ZOOOOMZ idea of an unified circuit board, which fits both type 2 and type 3 speedos. The double switch on the upper right corner will allow setting normal and calibration (speedo needle) mode, as well as the display in kmh or mph. Next step is to implement the board software and then go into testing.
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  7. ZOOOOMZ

    ZOOOOMZ Karting

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    Adrian, Wow, this is exciting! Great progress!
    I'm curious: what is the intention for the non-populated component CN1?
    I volunteer to be a beta tester, as soon as you're ready. I've pulled my failing speedo and replaced it with an interim one, so I can install your board and run my original speedo in the field as soon as it's ready... Thanks again for your work, on behalf of all of us with speedoblues....
     
  8. alhbln

    alhbln Formula 3
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    CN1 is the connector for flashing the firmware. I am using a pin grid connector so no need to solder anything to the board. Thanks for volunteering as beta tester! I'll try to finish a first version of the software after xmas when i have some spare time.
     
  9. chinook

    chinook Rookie

    Sep 2, 2009
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    Hi Adrian , congratulation for your awesomwe work and for share this work.
    We have a problem witch a speedo in a ferrari 328 gts 1985 , it works normaly but sometimes the needle reaches to the top in a counterclockwise , we test with a square wave (5V and 318 Hz)) and the result is the same, we test all the components and seems to be ok, any idea for help us, our circuit is type II.
    If yoou need a beta tester we are happy for help you, with de speedometer and speedo sensor , both are dismantle out of the car.
    P.D. sorry for my bad english, I live in Spain
     
  10. alhbln

    alhbln Formula 3
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    Hi Eulogio,

    question, does the needle also go to the top (12'o clock position?) when you are not driving, or only while driving?

    Does the ODO km/h counter at the bottom behave normally? This could also indicate a problem with the return spring of the Speedo needle, not necessarily an electrical problem.

    Best,
    Adrian
     
  11. chinook

    chinook Rookie

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    hi,
    The needle only reaches top when The car is running , and keep this position even if the car is stop only the needle goes to the initial position when de ignition is off.
    And the odo is working in all position of the needle. At the top of the needle is about 320 KM/h and the Odo is ok for this speed behave normally.
    best.
    Eulogio
     
  12. alhbln

    alhbln Formula 3
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    #162 alhbln, Dec 23, 2014
    Last edited by a moderator: Sep 7, 2017
    The needle and ODO in the type 2 speedo are driven by the same motor. If the ODO behaves normally then it might be a mechanical problem of the needle drive, which is based on a contactless magnetic coupling (see photo).
    On the other hand, if the needle goes back to the starting position when you switch off the ignition then it's most probably an electrical problem, but then the ODO should also misbehave.

    Not really sure what the issue is, to be honest. If you like you can mail me your Speedo and i'll have a look though.
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  13. chinook

    chinook Rookie

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    Thanks for your offer, PM sent

    Eulogio
     
  14. ZOOOOMZ

    ZOOOOMZ Karting

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    Hi Adrian,
    Just checking in to learn any news you can update on the speedo board project? I hear you've also been busy sourcing some "carpet" for the GT4 out there. My, you are a busy guy, aren't you? Thanks for your contributions to the restoration, care, and enjoyment of our Italian babies!
    ciao,
    Tim
    Zoooomz
     
  15. alhbln

    alhbln Formula 3
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    #165 alhbln, Mar 16, 2015
    Last edited by a moderator: Sep 7, 2017
    Hi Tim,

    thanks! I'm a bit behind schedule, not that much spare time the last months unfortunately. Still pondering the difference between the US and EU Speedo type 2/3 circuits, i though i had nailed it down but then got a EU 308 Turbo Speedo for repair where the circuit looks like an US Speedo, but isn't. But that i can manage in software later on, so not a big issue.

    For the development i build a test bench for circuit and software tests (left), as well as a Speedo type 1/2/3 tester (right) to check and calibrate Speedos. Using the tester i noticed that all of the type 2/3 Speedos i tested have a display error of around 10%, whereas the type 1 Speedos had a maximum error rate of up to 5%.

    Currently working on the board software, i can implement the motor driver either in software or hardware, will do some more tests what's best for reliability.

    Also received a 355 Speedo for repair, those are very similar to the 308/328 Speedos except that the circuit board has some more components for additional outputs. In theory the new circuit board could support 308/328/348/355 Speedos.

    Regards,
    Adrian
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  16. 2281GT

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    +1
     
  17. ZOOOOMZ

    ZOOOOMZ Karting

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    Adrian,
    Thanks for the update - for a guy who doesn't have much time to invest, you're sure making huge strides! Thanks again for your contributions.

    I'm curious about the display errors you're seeing - are they calibration choices, or is it non-linearity in the speedometer's response, so that it's possible to be accurate (zero error) at only one speed?

    Like I'd imagine many others, I'd like to be able to choose either zero error or some constant offset, like displaying real speed +3mph, so that I can minimize my chances of speeding tickets. I suspect, however, that these speedos are nonlinear, such that you could calibrate to read, for example, 74 mph when real speed is 70 mph, but the error is different than +4 at any other speed... How do the original designs behave?

    What is your design goal for the new board? Will your software compensate for non-linearity? Will you target to calibrate actual speed, or some offset? Will that be user-selectable, such that one could choose their offset?

    As an aside, there is a fellow Ferrarista here who is having speedometer issues with his 512BBi. I'll loan him my spare sending unit for diagnostics, but if he finds that his head unit is the problem, I suspect we may learn that there is yet another Type, beyond the ones you've already identified. I'll share his findings as soon as they're available.
    Thanks again for your hard work!
    -Tim
     
  18. alhbln

    alhbln Formula 3
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    For this test i've ignored the Speedo display (as this can be fixed by resetting the needle and adjusting the retainer spring) and compared the difference of the ODO display on one mile/km via the day trip counter. 2/3s of the Speedos i checked displayed 0.9 mile/km, some displayed 1.1 or 1.2 mile/km and some were correct. This was just a quick test based on sending the correct amount of pulses for exactly 1 mile or one kilometer. I don't think that this depends on the speed but rather on component variations in the analogue section of the motor driver circuit.

    Type 2/3 speedos control the motor speed with a hall feedback sensor, so there should be no problem with nonlinearity.

    A user defined offset (e.g. +3mph) could be done by manually resetting the needle position in the calibration mode. The ODO will be calibrated in hardware and is based on the embedded hall sensor feedback, so the supplied internal calibration generator is only relevant for calibrating the speedo needle position.

    Interesting, looking forward to this! Based on the production years i would guess that you'll find a type 2 board in the 512 BBi speedo.
     
  19. alhbln

    alhbln Formula 3
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    #169 alhbln, Apr 21, 2015
    Last edited by a moderator: Sep 7, 2017
    Some progress at last, i finalized the type 2/3 replacement board design (fingers crossed) and assembled a first board for development and testing. This board should support any type 2 or 3 speedo as used in the 308, 328, 348 and 355.
    Next stop is developing and testing the onboard software.
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  20. Crowndog

    Crowndog F1 Veteran
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    Sweet! I'm ready to test one or purchase one.
     
  21. alvaroagm

    alvaroagm Rookie

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    Thanks Adrián.
     
  22. Ferraripilot

    Ferraripilot F1 World Champ
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    Wow. outstanding stuff Adrian. thank you!
     
  23. alvaroagm

    alvaroagm Rookie

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    Adrián, we are looking forward to hearing about your advances . Thank a lot for your excellent work !
     
  24. alhbln

    alhbln Formula 3
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    #174 alhbln, May 11, 2015
    Last edited by a moderator: Sep 7, 2017
    So, the output/speedo motor control has been finished and works very nicely, should be even a bit more precise than the original circuit… sorry this took so long, i seem to be a bit short of spare time to do useful stuff like this these days.
    Next one is implementing the speed measurement for the incoming speedo sensor signal and solving the mph/kmh mystery.
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  25. alvaroagm

    alvaroagm Rookie

    Jul 7, 2011
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    Thanks Adrián!!
    Very very good work
     

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