AW4 Shift solenoid current draw?

[CheapXJ]

anyone know how much current these things draw?

I'm in the middle of designing a "tiptronic" control box for my XJ, and I gotta figure out how much juice I need to drive these things!

pretty much done with the electronics work on the logic level, I just need to build drivers for the solenoids and wire it up. (it's gonna be sweet, I even have a 7-segment display to show what gear is selected)

[5-90]

Drive them thru relays just to go easy on your solid state stuff - I think a nominal resistance value is 13 ohms, IIRC (I checked, once upon a time...) That works out to about a 1A draw, if Ohm's Law is not escaping me at the moment (hey, I'm set up for ballistics right now! Electronics was last week!)

I'd be interested in taking a look at what you've got in mind, if that okeh with you...

5-90

[CheapXJ]

http://home.ptd.net/~naumiler/aw4tiptronic.gif

gotta break it down into components, and I might have to throw a BCD -> 7 segment decoder in there, but it works flawlessly in simulation :D

(the little LEDs on the left represent the drivers for the solenoid sequence)

and yeah, one amp is a little much for some 74LSXX chips ;)

[5-90]

Yeah - but won't the 74LSxx sink enough to drive a relay? I think either that or an SCR might be a good way to go - but I prefer relays, they are easier to locate (for installation) and replace...

5-90

[CheapXJ]

I figured on isolating the logic outputs with an operational amplifier that's run off another stage of combinational logic. run the TCU SOL1 and SOL2 outputs into this stage and have the switch takeover here (but keep the nominal load on the outputs so the TCU still thinks it's controlling the tranny)

I just gotta work with how I'm going to do the "takeover" of the TCUs function... I want to set up the torque convertor in semi-auto mode (either automatically controlled alongside the tiptronic control, or full manual.) if I'm cruisin' on the freeway, I'd like something to pick up TC lock if I forget it ;)

So far, the progressis going good though. I'm also going to look into concerns with the wiring on later XJs to see if this will in fact work with their wiring as well, but have one box that'll do it all.

I'm actually surprised that nobody has done something similar to this, using logic control. sure, people do the switches... but this is just so much cooler :D

[5-90]

Lemme bang some ideas around and see what I come up with. I see no reason why you'd need the second logic setup for control - isn't the gate draw on SCR's measured somewhere in milliamps? Relays aren't much more - and you can do transistor gates to kick the relays closed, IIRC. It's not that I've got anything against logic IC's, but it seems there's better and easier ways to do the job...

5-90

[CheapXJ]

the thing is though, I don't want to kill power to the TCU.

granted I haven't cracked open the TCU yet, but I plan on getting one to work with (I'd like to make a plug-in harness for this, I don't like cutting into existing harnesses, and it can and will be avoided!)

I am going to use relays to drive the solenoids. I am however considering running the 7 segment display off the final drive for the relays, rather than running them off the BCD code that the counter puts out. since the AW4 doesn't start at "zero" in standard grey code to run the shift sequence (I can see why, if the TCU failed, it would be stuck in first :eek: ) and then derive BCD transpose "01" "11" "10" and "00" to "001" "010" "011" and "100" respectively, then use a BCD decoder to drive the 7 segment display.

I basically just started the actual design last night, so it's far from done, and I've already seen a few ways to reduce the number of chips needed in the original control design (me, being unobservant :rolleyes: )

I remember at one time you mentioned trying to reverse engineer some of the XJ's electronics, and anything info you think might be relevant would be awesome ;)

As far as operation of the complete project, this is what I'm going for:

one switch, to enable/disable the "tiptronic" mode

the tiptronic shifter itself (thinking either something similar to paddles on the steering wheel, or making the shift lever rock left-to-right to get the upshift/downshift sequence)

and one switch to control the torque converter. would either be automatic or forced lock (not hard at all, but keeping the TCU alive while truncating its SOL1 and SOL2 outputs is what concerns me)

I will keep you updated, you seem to be about the only one that shows a serious interest in something like this... which is hella cool :D

I could kick it over to some higher power CMOS chips, but then latency would be the killer. I really want to draw as little power as possible from the 74xx chips.

but don't give me too many ideas until after the 23rd... this is for my term project. why build something useless for just a grade, when I can build something for a grade, and get something I've wanted for about two years now ;)

[5-90]

Tell ya whut -
I've got a Renix-era TCU floating around somewhere - I think - and I've got a batch of FSM's spanning the years. Bounce me a reminder backchannel in a few days if you don't get anything from me, cos I'll scan what I have for TCU lines for your reference. I gotta figure out which boxes have the compleat set of 88XJ wiring harnesses as well, but I think something like this can be done thru a bypass tap or something similar - like what I used to do when I was wiring up vehicles with lighting controllers (patch in the plug, remove controller and plug harness together for OEM wiring configuration.)

Meanwhile, I'll try to toss around some ideas for running something like this in parallel with the OEM wiring, perhaps running it with an override to enable the secondary control? Kill the override, OEMR takes over. Offroad? Kick in the override. Something like that has to be doable. I figure wiring the override to kill TCU power and enabling some sort of indicator - bigger than Billy-be-damned and right in front of you! - so you are reminded to turn the thing off. Provision for most of that wiring is probably already in place, I'll see what I can dig up. Perhaps wiring it thru the Power/Comfort switch?

5-90

[CheapXJ]

I've got the diagram from an 89 for the wiring so at least I know it will work on my junk.

no reason to cut up good harnesses ;) I can pick up messed up harnesses quite easily and quickly, as well as damaged TCUs to rob them of the connectors.

I'll let ya know what I come up with as well. Hopefully I'll have the opportunity to build it on a proto board before too long (and not at my expense :D ) just to see how it reacts in the real world.

If you have Electronics Workbench, or Multisim 2001, I could send you a copy of the project files as well, I think it has some export filters so maybe other software will work too.

[5-90]

I think I got both of those somewhere - let me check and make sure. I saved the schematic you put up, so I've got that at least.

5-90

[Backdraft]

I don't know about anyone else here, but I think that is a very cool idea. I would also be interested in doing this, however I know NOTHING about electronics. Would you be interested in reproducing these and selling them once you get it complete and get the gremlins worked out, because I would be interested in paying you for your brainwork...lol. Maybe a tech write-up explaining it once you get it done as well if it aint too much trouble.

Mike

[Ed A. Stevens]

FWIW,

I burned 1/2 Watt diodes isolating the current to the solenoids. I changed my installation to relays for physical isolation of the TCU and override current (no problems since).

When the diodes burned the TCU went into limp mode: 1st, 3rd, 4th and no TC lock. No 2nd (unless you drove through the shift override limit in the 1-2 position detent) and no TC lock in the default mode. The limp mode will get you home, but the unlocked TC generates considerable heat.

I like your project, although I'll defer the critique to the EEE's (BSME only here).

When you get to the TC lock/unlock control, and speed sensor logic for the relay for auto mode, can you make the unlock speed setpoint adjustable? This would be a great addition to keep the AW4 cool in 1st gear (a locked TC is not available in 1st with the TCU program). Maybe something for a future term project?

Happy Trails!

[XJEEPER]

Another thing that has always bugged me is the fact that you can't just nudge the accelerator when cruising and get the TC to unlock when climbing slight grades or passing. I realize that the technology of my Renix era TCU can't match the tech that is in my 98 Accord, but I sure like the way it works. I'll be very interested to see how this comes out.

XJEEPER

[CheapXJ]

Originally posted by Ed A. Stevens
FWIW,

I burned 1/2 Watt diodes isolating the current to the solenoids. I changed my installation to relays for physical isolation of the TCU and override current (no problems since).

When the diodes burned the TCU went into limp mode: 1st, 3rd, 4th and no TC lock. No 2nd (unless you drove through the shift override limit in the 1-2 position detent) and no TC lock in the default mode. The limp mode will get you home, but the unlocked TC generates considerable heat.

I like your project, although I'll defer the critique to the EEE's (BSME only here).

When you get to the TC lock/unlock control, and speed sensor logic for the relay for auto mode, can you make the unlock speed setpoint adjustable? This would be a great addition to keep the AW4 cool in 1st gear (a locked TC is not available in 1st with the TCU program). Maybe something for a future term project?

Happy Trails!

From what I understand, the TC wouldn't really be able to handle the torque when locked in 1st gear. (thats what I gathered from reading this: http://www.wagoneers.com/XJ/tech/AW4-trans/tcu.html )

It would be nice to have that ability (especially when wheelin' ) but I don't know for sure if it'll handle it. I know how sensitive lockup turque convertors can be to conditions, that why I want it to default to automatic control when not forced to lock.

as far as auto mode for the torque convertor, the existing TCU will take care of that. It'll just be a relay controlled by both the TCU and the switch (diodes on both)

it's keeping the TCU happy, and out of limp mode that might me a problem.

I was thinking delusions of grandeur for another term project (plug in, programmable controller for renix FI that WILL output both running data and fault codes :D ) but that will be slightly more challenging ;)

:roflmao:

[CheapXJ]

Originally posted by Backdraft
I don't know about anyone else here, but I think that is a very cool idea. I would also be interested in doing this, however I know NOTHING about electronics. Would you be interested in reproducing these and selling them once you get it complete and get the gremlins worked out, because I would be interested in paying you for your brainwork...lol. Maybe a tech write-up explaining it once you get it done as well if it aint too much trouble.

Mike

There will be a huge writeup on my install. as far as actually building the circuit, if you can use a soldering iron, you can do it.

I'm basically just designing it around the 87-90 electronics. I have NO idea what effects it would have on later models, and I know that some newer XJs (OBD II ones, I believe) push fault codes and go into limp mode if you just do the low-buck 1-2 switch.

[Ed A. Stevens]

Originally posted by CheapXJ
From what I understand, the TC wouldn't really be able to handle the torque when locked in 1st gear. (thats what I gathered from reading this: http://www.wagoneers.com/XJ/tech/AW4-trans/tcu.html )

It would be nice to have that ability (especially when wheelin' ) but I don't know for sure if it'll handle it. I know how sensitive lockup turque convertors can be to conditions, that why I want it to default to automatic control when not forced to lock.

as far as auto mode for the torque convertor, the existing TCU will take care of that. It'll just be a relay controlled by both the TCU and the switch (diodes on both)

it's keeping the TCU happy, and out of limp mode that might me a problem.

I was thinking delusions of grandeur for another term project (plug in, programmable controller for renix FI that WILL output both running data and fault codes :D ) but that will be slightly more challenging ;)

:roflmao:


I remember when John was building his first TCU override control switch project (a long XJ-List project thread at the time), and this report is a good summation of the information available at the time (~1997), although some of the assumptions are not totally correct.

<When you come to a stop, either the TC unlocks itself (by nature of how the hydraulic plumbing works) or it bangs a bit, then stalls the motor... usually I flick the switch off before anything happens.>

If you test the AW4 without a TCU the TC lockup will not release through any "hydraulic plumbing" during a stop. It remains locked and is strong enough to stall the engine (I have done this). It is strong enough to stall the engine with a little rpm (1400 rpm, 4hi, and heavy brake application with the axles on stands, BTDT too). It will also smoke the brakes in 4lo. IMO, the locked TC lockup clutch can handle considerable torque, but may not be very reliable if subject to a high frequency of cycle operations (too much heat). Keeping it locked does not allow slip, and no heat, not like constant cycling or without any lockup.

<Putting too much foot into the throttle with the TC locked will give you a quick wake-up call... the TC lock is not intended to handle full engine
torque (remember where your peak torque occurs- fairly low...) and it'll give you a soft jolt if you forget to unlock before feeding too much fuel.>

The TCU appears to unlock the TC when sensing the brake switch, when sensing WOT from the TPS (sometimes), and at a set speed below a threshold as sensed by the speed sensor. There is a reference resistor in the wiring harness that must read by the TCU without bias (no shorting or bypass voltage) to have it lockup the TC.

Footing the moving vehicle at low rpm with a manually locked up TC provides no drama, just a slow progression of acceleration as you move through the powerband (the experience of my testing). I have to grant John credit, as I tested a near new TC, and maybe his TC was tested with 150K miles of wear and slipped (I would not discount what John experienced).

<One thing I will tell you about TC lock- The TCU is programmed to force TC lockup when engine RPMS are above a certain point (?dunno yet?), AND you're at Wide Open Throttle.>

My testing experienced that the TCU will be controlled to unlock at any speed if the brake switch is made. 4000 rpm, touch the brake pedal (short the TCU brake switch input), and the S3 is controlled to unlock the TC. No forced lockup rpm override.

I tried to get it to repeat a WOT unlock that it appeared to do in early tests, but could not, unless it downshifted first (drop to 3rd and unlock at the same time). When I was able to keep it in OD the TC would not unlock at WOT. I would like to hear what others have found in testing?

I did my testing with multiple VOM's reading the S1/S2/S3 voltage outputs, and the inputs to the TCU (backprobed connections on the TCU harness). The speed sensor can be backprobed as well (but I did not have a scope to count the speed of controlled unlock, what I want to be adjustable). I would recommend this exercise to help understand the TCU program sequence of operation.

I would like a failsafe TC unlock in 1st (with an adjustable slow speed unlock) to keep the temps down. The TCU unlock setpoint speed is too high (IMO, even with the 2nd gear override) and not functional in 1st.

I think you have a great project anyway (even if it fails to address an adjustable auto TC unlock).

[Backdraft]

CheapXP, thats cool with me. Mine is a 90 model, so i'm really not worried bout all the extra computer crap and faults. And thanks for planning on the write up.

Mike

[CheapXJ]

Thanks a TON for the info Ed!!!

I haven't had the opportunity to do any testing of my own, but I do know that currently my TC lock does do some funny things (may be due to having almost 315K miles on it :D ) and with that switch in comfort mode, I can feel it slip when getting on the throttle at lower speeds (feels like a plug randomly misfiring... about the best description I can give)

Mine generates a ton of heat, enough in fact to make the tranny blow fluid out of the vent while cruising at 70+ MPH when it was in stock form. I know almost nothing about the inner workings of the AW4, and having never torn one down, I'm just relying on info that I can find. some of the archives from the XJ List are excellent, but as you pointed out, they are dated as well.

Designing in the TC lock with an adjustible auto lockup/unlock speed seems like an excellent idea, and when I decide to expand upon it further within the next year or so, things will happen. It would be even better for those of us with high mileage junk compared to those with newer running gear.

I also thought about plumbing in a tranny temp gauge that would force almost constant TC lock at a certain temperature (basically anything above 10mph or so)

I guess another pipe dream would be to have multiple preset shift points along with one or two programmable ones... of course, only being a first year engineering student... I gotta learn how to do that first :D

Definitely alot of good ideas being tossed around. I'm not lookin to make money off of this, I'm all about learning this stuff. The plans will be available, and public domain. Information should be free!

[Lou]

CheapXJ,

Very nice work.

Have you considered contact bounce--do you need to debounce those switches?

The other thing is if you are going to add more functionality to this design, you may want to consider a cheap micro instead of discrete logic. Although, it is more fun designing it in hardware. Building in software is easier.

[CheapXJ]

I thought about burning a PLD, but using discrete components for a one-off design will prove much more cost effective for me. I'll be building it over summer vacation, and... I need the experience. This is really my first project for a purpose that I've designed from scratch.

I probably will have to de-bounce the switches. But I'll burn that bridge when I come to it (you don't get bounce in software simulations :D )

[ChicksDigWagons]

How has this project come along?

Just today I put together a working model of a sequential shift circuit for my XJ.

I'm completely cutting out the TCU however. I'm swapping in a 258 in place of the 4.0 that has long been missing from my engine bay (in preparation for a 360 also on the garage floor) So the TCU isn't going to do a whole lot of anything without any computer control inputs.

Thus the sequential push-button shifting.

But you could say I cheated. I used a Basic Stamp.

I was also wondering what the draw of the solenoids was. The Stamp can only handle ~25mA per output, or a ~50mA total output current. Most relays want >100mA on the coil. So I'm going to have to figure out something for that.

In the first draft of the software, I have it run sequentially through First, Second, Third, OD and then OD with the Torque Converter locked. I may add a stand alone switch for lockup as well as a crude fully automatic mode. The stamp is only useing 5 of its 15 I/O channels for this function, so I'm probably going to try to add some other perks as well.

[old_man]

OK you guys were talking about using SCR's to control the relays. I'm a EE/CS/ME with 35 years experience. I have one question, how were you going to turn off the SCR's? There are lots of ways to drive the solenoids, but SCR's won't work unless you use a capacitive back charge circuit.

I have the capability to lay out a pcb if you guys work out what you want.

[ChicksDigWagons]

I was considering using discrete components but I wanted it to do way too many functions. I'm going to drive a trio of relays with some npn transistors tied to three outputs on the basic board.

I did some testing and a PNP transistor is going to draw way too much current from the I/O to get the current for the solenoids. I have no idea how to implement an opamp either. (electronic hobbiest newbie here) I have yet to test an NPN, but I don't suspect I'll be able to get 2A out of it without far exceeding the I/O pins limits.

I also hooked up a 7-segment display. Its very nice seeing a numerical gear selection. I don't like the fact that one digit eats up 8 I/O lines. I'll either add a BCD display driver or just get a serial driver for my parallel 2x16 backlit LCD. That way I free up most of my I/O lines and have the ability to display meaningful data.

If I get a nicely working model I'll likely port it over to a cheap standalone PIC chip. I wonder if I can just get a PIC16C57C and program is with my Basic stamp board then use it separately...

[lugu50]

Dear Friend Ed:

As I can see maybe you are the only person who can help me. The case is that I need desperately a schematic for TCU installed on AW4 of my XJ Limited '88. Lot of trouble, had to change 2 transistors on TCU to correct reverse (which was not engaging on cold transmission, and now at last, 1-2 gear will not engage not in Drive lever position , nor in Lever 1-2 position. If I disconect TCU. 1-2 gear will engage.

Any help and or advices will be very apreciated.

Thanks,


Luis


FWIW,

I burned 1/2 Watt diodes isolating the current to the solenoids. I changed my installation to relays for physical isolation of the TCU and override current (no problems since).

When the diodes burned the TCU went into limp mode: 1st, 3rd, 4th and no TC lock. No 2nd (unless you drove through the shift override limit in the 1-2 position detent) and no TC lock in the default mode. The limp mode will get you home, but the unlocked TC generates considerable heat.

I like your project, although I'll defer the critique to the EEE's (BSME only here).

When you get to the TC lock/unlock control, and speed sensor logic for the relay for auto mode, can you make the unlock speed setpoint adjustable? This would be a great addition to keep the AW4 cool in 1st gear (a locked TC is not available in 1st with the TCU program). Maybe something for a future term project?

Happy Trails!

[kastein]

Since this thread has been awoken from the dead...

I find this subject very interesting, as yet another EE/CompEng type. I'd look into building something neat, but I have absolutely zero understanding of how the transmission control signals actually work and make the transmission shift. Anyone care to enlighten me, as a complete transmission n00b?

As for driving the relays, I would probably use IRF511 N-channel MOSFETs in a ground side switch configuration, as they are cheap and readily available. Remember to install properly rated back-EMF clamp diodes across the relay coils or you WILL lose the MOSFETs. If the relays require less coil current than I think they do, Supertex VN0300s might work, and they have the benefit of being small and cheap (in fact Supertex will send you ten samples for free if you ask them!)