DIY Perfect Pass

[turbohoje]

hello all,
i'm new to boating and am learning about all these fancy toys they can have. one of which called a perfect pass.

in my boat, when pulling a wakeboarder at 22 mph (gps speed) the boat is right on the fence about falling out of plane or staying up and speeding up to 25+. so when driving, i have to watch the speedo like a hawk and make slight adjustments to the throttle all the time to keep the boat at the best speed for the boarder.

so this is fine and good for everybody else that ski's off my boat, but nobody seems to do as good of job for me. the throttle is very much not a set-and-forget at 22 mph and i spend an undesirable amount of time telling the driver to speed up or slow down.

are there any tricks for this? the engine rpm is right at 4000 at full throttle and it has no problem popping out of the hole. I considered dropping the pitch or going to a 5 blade prop.

my engineering side makes me want to try and design a diy perfect pass. not knowing how they work, this was my idea:

1) disconnect the throttle cable at the carb and connect it to a belcrank with a rotation sensor.

2) add a servo to control the carb's throttle

3) use a small embedded device to read the GPS speed off my garmin, and make adjustments to the throttle as long as the input throttle is not set (in cruise mode). if not in cruise mode, just re-produce the throttle input on the rotation sensor.

odds are i'm over complicating this, but would have a fun time giving it a go. anybody know how a proper perfect-pass controls the throttle?

thoughts?

Justin

[vette74]

A couple of people have tried this using cruise control from a car that reads only RPM from JC whitney. But I think they had limited success it doesn't cycle enough and the speed varied too much. I was in the same situation as you I finally broke down and bought a used perfect pass system.

http://www.jcwhitney.com/AUDIOVOX-ELECTRONIC-DASH-MOUNT-CRUISE-CONTROL/GP_2001597_N_111+10201+600000570_10101.jcw?reviewflag=1

[turbohoje]

gotcha,
i was first thinking that i had an incorrect setup of the boat or something along those lines why it would happen in the first place.

my guess is that car cruise would over control the throttle all over the place. such as, the boat would have to fall out of plane drastically and sit back down in the water before it would start to load the prop enough to slow it down. secondly it could not accurately determine the speed of the boat just by rpm.

just for kicks, i found that i can talk to my gps and get speed out of it no problem. there are two ways to do this. at best, i can get velocity (as a vector) every second.

so my next question: what does a used perfect pass sell for? if its still more than i'm willing to pay for my old boat, how doest it interface with the throttle? i imagine you can just grab the throttle and slow it down on an emergency right? Does the PP actually move the trottle linkage?

[vette74]

I think I have about $700 in mine. The way it works is that a separate cable is connected to a servo motor and pulls the opposite way of the throttle cable and adjusts the speed accordingly. When a rider falls and you slow the boat down the perfect pass cable becomes "loose" and the throttle cable is in control again. Then at some point the servo takes the slack out of it again and when you throttle up and you get near your speed it takes over again.

[GuitsBoy]

Head over to perfectpass.com and read through all the manuals and other documentation they have alying around. Basically they use a stepper motor to tighten the throttle. You put the hammer down and accelerate, once it hits the desired speed or rpm, the step motor allows the throttle cable to start to pull away from the actual carb linkage in order the slow acceleration. Then if it slows down too much, the stepper motor will tighten up teh slack and pull the carb linkage closer to the throttle cable. Thats why you have to throttle past the speed you want when using perfectpass.

I too explored some options for using a car cruise control. It would be difficult fo rthe cruise control solenoid to be forceful enough to overpower the friction in the throttle control lever. Also, when you throttle back to neutral to pick up a down rider, the DIY cruise control will still try to speed up. And lastly, you will likely run into endless hysteresis and attack/decay issues that lead to severe overshoot / undershoot. If youre proficient enough in this area, im sure you could hack an automotive cruisecontrol to do what you need, but it may warrant almost a complete redesign. But if you do decide to try it, make sure you take pictures and publish a writeup for everybody else.

BTW, you might be able to pick up a perfect pass cruise (RPM only) kit used for around 400 bucks. I started off using a cruise system I pieced togather, and it worked pretty well in my old 18 foot four winns. Now we stepped up to perfect pass digital pro in our mastercraft and havnt looked back.

[turbohoje]

thanks for the input. i wasnt sure how a perfect pass did it.

what i like about that design, is that if the system fails for whatever reason, the driver can still cut the throttle.

making a sliding apparatus for the throttle cable wouldnt be as big of a deal if i still had access to the fab labs in college, but maybe its more simple than i think.

my thought was to fully disconnect the throttle from the carb and make it drive a sensor. i'd be happy to go into how i would do that.

next, the throttle would be driven by a heavy duty servo from the hobby shop.

both the sensor, servo, dash button, and gps hook into a small micro controller.

how it would work:
the microcontroller will re-produce what it sees on the input side of the throttle on the servo when not in cruise.
when in cruise (get to desired speed, press button), it will maintain speed unless the user side throttle is moved at all - at which point it goes to the mode where it just re-produces the input throttle.

i figured this was easier but the more i think about it their idea is far more simple. i dont even need any sort of throttle sensor. if the driver slows it down, the DIYPP may attempt to go faster by removing slack but it doesnt matter since the highest setpoint has been dropped.

[turbohoje]

ok i officially started the project. I have some parts on order, and might be playing with a working prototype in a week or two.

i'm expecting it will hook up just like the perfect pass. i'm going to drive an RC servo (at least for the prototype) that will control the 'back-off'.

i have successfully talked to my garmin 60csx and read the speed and velocity vector off it. on this particular unit, there are two methods for getting the speed.
1) NMEA spec (this is common for connecting to other units)
2) text: this is much less chatty and is very simple.
I can read both w/o a problem, however the NMEA data only comes out every two seconds, and the text values come out every 1.

If anybody out there wants to help with this project and has a gps with a serial out, i'll make you one for the cost of parts. i would like to test other gps units to see if they communicate in a similar fashion to find out what the most common communication denominator will be.

Plug for the 60csx (might fit other models too)

there are a couple others out there, but the test will only use 2 wires:
ground, and data-out.
the final version will supply a 6v charging voltage for the unit and will use 3 pins.

i'm at
turbohoje@hotmail.com
if you want to get your hands dirty with a electrical/robotics project

[tuxedosteve]

I may be late to the game here, since it looks like you've already begun your project (any updates?), but here's what I put on my 19ft. Sea Ray 190 sterndrive which cost me a mere $60 duckets - http://www.sesport.com/5_29.asp

I plane off the holeshot much faster, even with about 800lbs of ballast and a boat full of people and I can maintain speeds as low as 18mph without issue. Before I put the foil on, I could barely plane at 22-23mph. It's so nice being able to set the speed with just my throttle and leave it be until my wakeboarder falls.

Having been behind a real wakeboard boat (my neighbor's 21' Tige) with a perfect pass, I have to say it's very nice to simply throttle down and let the speed control take over, but I just can't justify the cost or the time to develop a cheaper solution when the hydrofoil works just fine.

[WakeMikey]

Yes if you are running a Glastron the hydrofoil is one of the most important upgrades you can have according to the other members here. Even better than a 5 blade prop. Gonna make my friend get one this summer.

[turbohoje]

thanks for input. i have one of those foils but i have not yet put it on. it was given to me from a guy who said that it didnt do anything. i was going to use it as a step to make it easier to get into the boat hahah. seems to me like it would have an effect when trimmed down a bit. the hydrofoil i'd like to put in the boat is made by sky ski.

as for the pp project, its put on hiatus at the moment. i discovered a cracked lower unit housing yesterday when i got the boat out of storage. looks like i need to tend to that before anything else.

otherwise i have a pretty good start on the DIYPP. once the boat is operational again i'll have a chance to do some more testing the code that runs on a laptop. after that works pretty well, i'll port it over to run on a PLC.

if you have any desire to play with the alpha version, you'll need:
1) some time and a strange desire to tinker with things
2) a laptop with two serial ports (usb dongles ok)
3) a NMEA gps antenna with a rs 232 port
4) pololu ssc03a servo controller
5) a servo hooked to the throttle cable just like the real PP setup. the servo controls the 'back off' of the throttle by adding slack to the linkage.

[turbohoje]

I'm sitting at the inspection station (much like the bouncing souls song) and am bored so ill do a little follow up on the state of the code.

I have a small c++ program that parses the nmea xml text from my gps unit. It gets the speed vector every two seconds. The c program also communicates to the pololu servo controller via another rs 232 serial port on the laptop. When hooked up, the c program will move the servo as the speed vector exceeds the desired speed entered on the laptop screen.

The program had a tendancy to 'hunt' continuously for the speed. By this I mean it would reduce the throttle by a factor until the desird speed was met, but by this time it would be too slow and would then increase throttle until desired speed was reached again, but may have been too fast.

To counter this I made a calibration of the backoff to desired speed. This was done by making the boat go full speed then stepping the backoff a degree at a time and recording actual speed. This way when the desired speed was met, it would go to the pre determined backoff and make only small adjustments from that point on

This seemed to work well however it is dependant on my boats speed characteristics, and the driver putting the throttle in the exact same "full" position each time.

What this means is I need to either come up with a method that matches speed without hunting, or will have a method for auto calibrating. I would rather do the first.

Ill be happy to share my code in an as is state, but mind you it will take some massaging for your setup. Another option is wait for me to get my boat running and ill make some fixes to be more "other boat" friendly.

[polkaking27]

turbohoje-

this thread is really interesting. I think what your doing is great. I'd love to get in on testing out your code, but I don't have the slightest idea what you are talking about with all the "smart guy" lingo. Anyway, I'm glad there are people out there that can understand this kind of stuff, so us "less smart" guys can have a plug and play PP unit to install in our boats.

Good luck with the project, and keep the updates coming

[polkaking27]

turbohoje-

this thread is really interesting. I think what your doing is great. I'd love to get in on testing out your code, but I don't have the slightest idea what you are talking about with all the "smart guy" lingo. Anyway, I'm glad there are people out there that can understand this kind of stuff, so us "less smart" guys can have a plug and play PP unit to install in our boats.

Good luck with the project, and keep the updates coming

[turbohoje]

boat is still frozen, so no updates as of yet.

when the boat passes its maiden voyage test, i'll make another one and document the process so its easily reproducible. that way its easier for the rest of you to take a stab at it and get back to me with improvements.

[smitty1258]

update?

[turbohoje]

just got back from mexico, got a vm saying the lower unit rebuild is done. i just need to pick it up and con a buddy into helping me lift it (upper/lower assembled) to put it back on.

then i can put it in the water, and resume development.

[grip01]

Turbohoje,your going about the cruise control the wrong way.In reality its very simple and straight foward with the same theory through all models and manufactures.
For starters the boat cruise works on the same platform as the car cruise.It takes one or more signals and make choices to acheive a constant hold.
These signals are pulse like the tach pulse and the vss(vehicle speed sensor)much like the pulse from a paddle wheel or the pulse from a nordskog gps pulse generator.
Most aftermarket car cruise controls are variable to compensate for different models and can be adjusted for many applications so in theory if you connected the nordskog to a css100 audiovox and the tach it would hold true with the gps.Also css100 can be adjusted to react faster or slower allowing you to dial in your throttle response.
The reason people have been unsuccessful with the car stuff is because of the safety features built into the cruise.For instance its set to not ingage before thirty miles per hour and can be over come by raising the pulse count on the module.Also it has a ground loop safety on the brake light wire that has to be grounded when engaged and positive to disengage which can be solved with a few relays.

[grip01]

In case you didn't know the nordskog pulse generator is a gps unit for offshore speed boats and streetrods.It simply takes the signal and turns it into a pulse that can be read.
The css100 is a audiovox cruise control.

[turbohoje]

grip,
thanks for the feedback. i'm not sure i know how the aftermarket speed controller works well enough. i imagine the cable linkage would have to sit in between the throttle linkage and the carb to add a small adjustment (which should be all that is necessary).

the fundamental difference that i can conceive of is that the car cruise would normally tug on the throttle and allow the return spring to close the throttle. i dont believe that you can operate the throttle from the engine side without bending something - as in having the control servo move the whole linkage back to the drivers console. i would think a break away would also need to be in place so the driver can always take control over the cruise. maybe thats not such a big deal bec the ignition key is right there too in case the speed control ever fails or sticks.

i'm not sure though, i have never played with and aftermarket cruise. given my understanding of them (and the description on jcwhitney), i assumed i needed something else.

the nordskogg device is very cool!
http://www.nordskogperformance.net/product.php?productid=18763&cat=5&page=1 that actually takes care of a lot of what i would need to diy pass to do and it comes packaged in a sleek dash device. i totally understand that it generates a square wave and you interpret your velocity based on that signal just like you would an optic sensor. my only beef with it is that its more than i'm willing to spend on a diy perfect pass. if i'm going to drop that much on materials, lets say $500 for gauge and $200 for auto cruise control i'm already in the perfect pass price range.

this is what i was expecting to use for a speed sensor:
http://www.thegpsstore.com/Garmin-GPS-18x-serial-receiver-for-PC-P1842C11.aspx it much more cost effective and delivers the speed (or vector) as text in xml every 2 seconds. i have a garmin 60csx that has a serial port on it, so i dont need one of these for development, but i plan to build one in eventually.

there are some displays here http://www.crystalfontz.com/product/CFA633-TMC-KS.html that are relatively inexpensive and they have buttons on them. i'm expecting that i can display speed, set speed, perhaps timers, distance traveled, temp, lake temp, engine hours and what have you on this screen. here is a diy temp sensor for a serial port and these devices can operate on a bus http://martybugs.net/electronics/tempsensor/hardware.cgi also if i open source the project perhaps other hardware hackers out there will develop new features. i'm a PLC programmer by profession so its easier for me to write code than it is to do mechanical stuff.

do you know of an inexpensive speedometer that expects a square wave as an input? just in case a builder doesnt want to go the whole display route, perhaps an autozone part (or two to display set speed) stand in its place. i would then generate the square wave for the speedo from the PLC.

personally i would like to cover up half of my broken or inaccurate gauges i have on my boat or turn them into cup holders or something.
another blue sky idea would be to throttle back the boat if an engine temp sensor goes out of range. my boat isnt equipped with alarms for heat (or a reliable temp gauge for that matter). sometimes my guests when driving dont watch or know to watch / listen for some of these things.

if anybody has gone the car route (or any for that matter) before, let me know how it went. does an aftermarket perfect pass need any sort of calibration?

i might have to wait a week or so to get paid before i can re-active my boat. my lower unit case freeze was more expensive than i expected it would be. after that, as promised, i'll post some more informative pictures than ascii art.

[smitty1258]

bump

[turbohoje]

ok finally an update.

the boat is STILL in the shop. once it was finally done, the bill was $1500 and I wont have that until tues/wed before i can get the lower unit out of hawk.

on a side note, i did stumble upon http://diydrones.com/. they have a product there called the ardupilot that has a direct interface to a GPS and has a servo controller built in.

the most beneficial part of this whole story is the cost:
$24 PLC http://www.sparkfun.com/commerce/product_info.php?products_id=8785
$15 USB Interface http://www.sparkfun.com/commerce/product_info.php?products_id=718
$60 GPS antenna http://www.sparkfun.com/commerce/product_info.php?products_id=465
$26 LCD display http://www.sparkfun.com/commerce/product_info.php?products_id=813

there will be a little hardware needed like a servo, wire, voltage regulator, rocker switches, but all in all materials will be sub $200

it has plenty of analog ins, and also has PWM inputs so that might easilly connect to a HET (hall effect transistor) for RPM sensing.

ive got the lot on order, and will be porting my code over to I²C as soon as it shows up.

hardware hackers give me a shout if you are interested. turbohoje@hotmail.com is my landing email.

Justin

[smitty1258]

bump Im really interested to see if this works. Maybe you should post this over at WW to see if there is anyone there who has the hacking skills to help?

[turbohoje]

yeah i figure i will post it on hackaday.com once its working on the new hardware.

i STILL havent got the boat in the water. there have been a few hangups on the lower unit (being $500 more than i was expecting) and my trim tilt cylinders were blown out.

here is a pic of the hardware in case anybody was curious



that is everything but the servo, linkage and power supply. that display is 4x20 characters. i'm going to start with current speed, set speed and clock.

[turbohoje]

ive been messing around with the display. the new gps is integrated and i have not got the gps sentances parsed yet.

here's a display idea i have been kicking around


i have decided i'm going to sense engine rpm as well. i think it will help for getting the speed right first try without hunting. i think it could be used for greater accuracy when within 5 mph of the target. the gps has takes a second to catch up with changes, but the rpm change will happen almost immediately.

what is worth putting on the display?
target speed, current speed, time, rpm, heading, odometer, trip meter, water temp, engine temp.... or is there a better use of screen real estate on something i havent thought of? to get lake water temp, i was going to put a sensor inline with the fresh water intake to the motor as it comes off the transom plate (i have an IO). This should work right? The water shouldn't have changed temperature that much in the lower unit but it might rise if you sit still as the engine area warms it up.

your thoughts?

for the display i'm going to get a piece of plexiglass and cut it to fit in location, then mask off the viewable part of the screen and paint the rest black. it should look pretty decent and be weather proof. Others will be able to fit this display in a 4" gauge cutout. but the PCB will have to sit behind the dash.

[smitty1258]

[Cyclonecj]

Justin,

Awesome project!! I have an inop (buttons don't work) PP display gauge I could sell you cheap. It might not be worth the trouble to try to use it but it would make a good mount for your display. It would fit one of the large holes on your dash and it is the generic display, no boat brand name on there.

Also, there is(was?) a company called Accuski that made a boat cruise control system that had some really unique features. You could set it to automatically pull up a rider, and it had a big red foot button to engage/disengage etc. The system didn't work well from what I understand, and at least a couple of guys on my site have removed the system and installed PP. I'm sure you could purchase the accuski hardware cheap if you wanted it, there's a servo and throttle linkage hardware made to hook up to an existing throttle cable.

The manual for accuski is posted on my site here

http://www.epicmarine.com/docs/AccuSki%20Operating_Manual9_0.pdf

If you go to my forums and post for accuski hardware, somebody will offer it up;)

Hope that helps, good luck.

[smitty1258]

personally I like the idea of common hardware, so what anyone can just build one of these and not have to hunt for used existing maybe hard to find parts.

[jwroblew]

I'm very interested in this project. I have a PP (RPM based) system now but I'm not thrilled with it, I like the pull and the fell of Zero Off, (the GPS system) but can't upgrade my boat, plus it's very expensive. Here is what I was thinking about doing.

1) go with a Perfect Pass stepper motor setup, pull cable to add throttle let return spring take away throttle

2) get a 10 hz GPS chip, better sampling = less hunting for speed. I believe Zero Off uses two 5 hz units, this probably has some advantage over one 10 hz.

3) tie into Throttle Position sensor (TPS) , I would calibrate TPS for some known speeds, this way the system would have some place to go first before adjustments are made by the GPS. Since I am a skier I would calibrate to all slalom competition speeds. The calibration would be a one time thing. Also this could act as the off switch, pull back on throttle "x" percent would disengage the system. Starting close to the correct throttle position and a quick sampling rate should eliminate most of the hunting, add some filters to eliminate the rest. On older boats with out a TPS sensor you could add your own sensor.

I would let the system engage a few tenths of MPH faster then the desired set speed, than take the TPS to the calibrated position, maybe even a small percent greater than the calibrated position, since the pull from boarder / skier is bound to add more throttle. Than let the GPS signal tell the system to speed up or down.

You could also then add some other tuning parameters, such as ramp rate of throttle. You could also have the system learn average throttle position when boarding/skiing, which would over right the baseline, giving a better engagement.

[turbohoje]

yeah i'm totally on top of the learning of the throttle position, however in my setup its dependent on backoff so the throttle has to be in the same place (100%) each time. once a speed is set its stored in the flash.

i'm in the middle of a quarrentine period at my lake so i dont get to play until next week. i'll post more as i get started.

[jwroblew]

If your looking at the TPS sensor your initial throttle position should not matter. TPS sensors either work off of voltage or resistance, so let's use voltage for an example. At zero throttle you see zero volts, full throttle you see 12 volts and no rider you see 8 volts at 20 mph. So you throttle up you will over shot the 8 volts on get up since you will probably be close to wot, at 15 mph the system engages and the servo motor moves the throtle linkage untill the TPS sensor sees 8 volts. Then the GPS takes over from there. Of course you could get the system to learn average voltage for the speed your going with a rider, so in the example above 20 mph no load was 8 volts and maybe with a rider it's actualy 8.5 volts. So that would be your initial start point. I would stay away from RPM because it takes the system forever to settle in.

[jwroblew]

If you have a boat with out a TPS you would have to add one but you could come up with something really cheap. Then you wouldn't have to worry about initial throttle position

[smitty1258]

bump

my marriage needs this!

[turbohoje]

TPS sensor HA!! perhaps you didnt look too closely at my boat. its a 1980's carburated gem of american engineering. you are correct tho, the tps would be a great place to get an idea, however i almost think a square wave is easier to deal with (from a HET) off one of the ignition wires than an analog. mag rotation sensors work really well but then i'd have to come up with a bellcrank and a linkage. there are also sonar proximity sensors that would work well for linear things too. i'd like the easiest method for installation so that others are not intimidated by putting this on their boats.

i'm not sure if a rpm or a tps sensor would be easier to code against. correct me if i'm wrong but here are some scenarios:

TPS sensor:
once a known throttle for speed is found, that value from the tps could be stored. when accelerating and the boat is nearing the desired speed, or the instant it reaches the desired speed the backoff can seek the last good throttle position checking against the analog off the sensor. when everything is fine and good, the most recent position is constantly logged for that set speed. otherwise without a known value it will back off on increments to learn the speed.

if the rider of the boat pulls really hard or the boat turns against wind or something and the load on the boat changes, the change will have to be reflected via gps and adjustments will be made to the backoff off the throttle. these adjustments may be different for each boat so a universal 2% change may hunt. (2% is just for args sake).


RPM:
same scenario, the boat is slowed and the gps notices a change in speed. increasing the throttle (or decreasing backoff) can happen by a known incrment of so many rpm. this way it is less likely to hunt since it will be easy to not terribly overshoot adjustments.

perhaps these things get learned as well: 1mph slow - increase 200 rpm, 2mph slow, increase 300 rpm etc. the opposite might be, 1mph slow, burst the throttle by 5% and wait for a change. i also figure motors will rev up at different rates and it would be nice to not burden the user with lots of configuration options.


your thoughts?

[smitty1258]

rpm sounds the way to go.

Im ready to be the second tester, you being the first

my wife has a hard time keeping our I/O at a decent speed, and it drives me INSANE!

I am however thankful that she pulls me at all

[smitty1258]

bump