2nd Gen Non-Engine/Transmission Where can I find a 5 volt source?

[Allnew2Me]

I'm playing with my BanksBrake to allow it to be applied manually and have so far figured out that I can take advantage of one of its features to get another. When the engine is cold the brake comes on manually sensing the voltage at the coolant sensor, but will release whenever the accelerator is touched. Once the coolant sensor lowers the voltage by the engine warming, the brake goes off and stays off until the computer senses the need to apply it and lock the torque converter.

The brake works well but when driving I am limited to the Banks parameters which don't allow the brake to come on at certain times that I would like to use it.

If I can find a source of 5 volts, I can apply this to the coolant sensing wire that feeds the Banks controller and will be able to turn on the brake when I want to, but still have the safety of the throttle-off feature which is designed into the Banks controller and keeps the brake open whenever the throttle is at anything but idle position. I will use a SPDT switch to disconnect from the coolant sensor so as not to backfeed voltage into the PCM when using this. A mystery switch will take care of the TQ clutch.

So, does anyone know where our trucks supply a key-on 5 volts?

I could have avoided all this fun if only I bought the three-pedal model!

 

[WKruger]

Tie in a few resistors to a 12v source.

 

[Allnew2Me]

I did think of that, and actually tried all the small ones I had but nothing that dropped it low enough. Any idea of the correct value to do so?

All of our computers seem to run on 5 volts so there has to be a source I would think.

 

[WKruger]

Voltage regulator? You could tap a wire off one of the sensors, but it'll probably end up throwing a code or fry something.

 

[Gary - K7GLD]

A cheap and common Radio Shack 5 volt regulator chip will easily provide stable 5 volts for what you want - and NOT interfere with or compromise other systems in your truck...

 

[Joe G.]

If you have a wiring diagram you can find a 5 volt supply on the PCM. Using it depends on how much your device will draw. If it's not too much then the voltage supply for the TPS should work. If you want the schematic for a simple 5 volt supply using a chip I can send you one.

 

[fest3er]

Radio Shack should sell 12VDC to xVDC converters. They are often switchable among several voltages. Or, as Gary suggested, use a DC-DC converter IC. Use a diode to prevent backfeeding the PCM. Depending on how you use it, a single pole momentary contact switch might better than a toggle switch.

 

[Allnew2Me]

Thanks Gary, that is ideally what I would like, an independant supply. I didn't know there was such a thing as that regulator but will stop by to see if my local RS has one.

Joe, I have the shop manual but wasn't sure if the supply was able to be tapped to use independently, although in the Banks application that is what it does, it feeds the Banks controller with a coolant-sensor-controlled 5 volts that diminishes as the coolant warms. I would appreciate the schematic for the chip you mention in case I am unable to find a ready-made version. Thanks again.

fest3er, I am safe using the SPDT (I said SPST in the original post but meant SPDT) switch in this application because the Banks controller already is designed to release the brake when the accelerator pedal is touched. I can leave the brake on and it will just cycle on and off with the pedal use which will keep it from being on when giving her the fuel, not a good thing. I am considering using a momentary switch with the TQ lockup switch so I can apply the lock/brake and not have the TQ locked all the time.

 

[SSolderitch]

in the model train hobby - DALLEE electronics, Reading PA. Has a constance supply voltage regulator. It is made for AC/DC and is made to go from 20v down to 1. 5 (for led's). the voltage is marked on a pot you can adjust, however a meter would be the best way to check the actual voltage cumming out of the unit. It is a very small package (1" x 1") and is under $20.

 

[Joe G.]

Joe, I have the shop manual but wasn't sure if the supply was able to be tapped to use independently, although in the Banks application that is what it does, it feeds the Banks controller with a coolant-sensor-controlled 5 volts that diminishes as the coolant warms. I would appreciate the schematic for the chip you mention in case I am unable to find a ready-made version.

Email me at -- email address removed -- and I'll send you the schematic. Pretty simple thing to build.

 

[Allnew2Me]

After doing a little more investigating, I found that the ECM has two 5 volt supplies that power the CPS, APPS, IAT, MAP, oil pressure, and Coolant temp sensor. The PCM uses pin 31 on module (plug) C2 to supply 5 volts to the transmission solenoid.

I am going to try using this to activate my brake.

 

[PRout]

In the long run, a separate supply would be better because there are any number of things that can happen, loops, transients (spikes), noise, emi/rfi whatever (that can effect the expensive ecm).

If it were me (be glad you're not), I'd build the regulated supply using one of the regulators mentioned above, build it into a nice little project box, include a fuse at the point of its source of power and a micro relay inside the box to turn it on/off. Fuse the output circuit also with a fuse holder built into the box to keep it clean. Mount it behind the panel under the steering wheel for easy access. Run a pair of wires to a mini-toggle switch located wherever is convenient for you to turn on/off the micro-relay and you have not added a new variable to the sensitive ecm, but can activate the brake at will with the small toggle switch and let the relay & regulator do the work, not the ecm.

Sheesh, if you can understand this, you're a better man than me. :-laf

 

[Moose Truck]

After doing a little more investigating, I found that the ECM has two 5 volt supplies that power the CPS, APPS, IAT, MAP, oil pressure, and Coolant temp sensor. The PCM uses pin 31 on module (plug) C2 to supply 5 volts to the transmission solenoid.

I am going to try using this to activate my brake.

Here is a BMP of the transmission 5V wiring at the PCM. My truck now uses a DTT Power Supply for the transmission, so mine is unused. Moose

 

[Gary - K7GLD]

Picking voltages off the ECM or PCM to use for other vehicle uses is NOT a good idea - too much potential for "unintended consequences" - which would you rather replace in case of "accident" - a $1500 ECM - or a $5 separate power supply?

 

[DieselDoghouse]

What Gary said—I been (grew up) around electronics too long to know that tapping regulated digital v+ (5. 0V) to another use can do BAD thengs. Many times these busses are current sensing as well and increasing I-out will upset them—badly. Any one of the 5. 0V IC regulators (the old National LM317 series) will give you clean (ripple-free) output as a separate source. Then as mentioned be very careful where it goes. IF you backfeed v+, even intermittently, BAD things happen (you let the smoke out of parts). You will likely need one OR MORE diodes to block backfeeding. BUT, there's more!! IF those diodes cause a voltage drop for the forward-feeding (OEM) voltage path error codes will ensue—hey aint this FUN??. As my Dad used to say, think of all the data states you will encounter, then rethink them again. (He wasn't touched, he was an engineer. )

 

[Allnew2Me]

Thanks guys for the input.

Phil, yes I do understand what you are saying and that is how I like to approach any of my projects, try to do it once right. I am very comfortable with electrical stuff until it gets in the electronic rather than the electric, hence my original posting.

Moose, thanks for that schedule, I have the shop manual and found the same page to take a look at and try and figure this out.

Gary and Dog, after thinking about this when I do my best thinking (when I'm supposed to be sleeping) it did occur to me that I might introduce a new "sensor" into the picture and the PCM may see this as a reason to throw a code or worse. I was going to breadboard the PCM trans supply to see if it would trip the brake controller but I'm glad I have not had the time to do that yet. I talked to Banks and they did confirm that the application of the 5 volts would indeed activate the brake with no other foreseen problems so that is nice to know.

I also have a schematic for a supply using the 7805 chip and bought one at RS to play with. I will go the safe route and build the supply, fed and fused from my existing key-on auxiliary panel.

So this is one half I think that is solved. Now the next issue is the mystery switch and how to wire it to allow the locking of the TQ in all gears so I can use the brake in first if needed. The reason for all this is that the Banks controller will not activate until vehicle speed reaches 30MPH and won't work in first gear. I often find that going down steep winding Sierra grades does not allow that speed to engage the brake so I'm looking for a way to use it when I want to use it.



Thanks again to all for the help.

 

[PRout]

Dont know if this link will work or not but this looks interesting. .

V-Infinity | DC-DC Converters | VBD10-D12-S5 : 10W, 5V, 2000mA, single output, isolated DC-DC

The site is: V-Infinity - DC-DC Converters, AC-DC Power Supplies, Custom Power Solutions

Part Number is: VBD10-D12-S5

Description: 9-18v input, 10W, 5V, 2000mA, single output, isolated DC-DC

Sorry, its made in Taiwan but what's new...

 

[Allnew2Me]

Okay, I built the 7805-based voltage regulator and it works great. I have a clean, indepenent 4. 99 volts. I can now manually apply my Banks brake and still retain the safety function of having the brake release whenever the throttle is touched.



I had planned on just leaving the supply on when the key is on, it only draws 3. 5MA with no output load on it, any problem with this? I can switch it with the brake activation but it would be a simple thing to just leave it on. On the bench it doesn't generate any noticable heat.



Now the next project is figuring out which of the several torque convertor lock switch schematics will allow me to lock in all gears, but that is another post.



Thanks to everyone for all the help with this!