Hi, I recently found this site and although I don't have a diesel to convert now I hope to in the future.
Anyways, I don't know if this has been discussed before or if someone has already done this, but I drew up a quick circuit to automate the fuel switchover on systems like FattyWagon which have true return lines for the SVO. The vehicle must also have independantly controllable solenoid valves for the send and return lines.
I created the schematic with CirCad98 and if you do a google search for circad you'll find that you can download a free evaluation copy. Sorry, I don't know how to export it to a common graphic file (anyone who can convert it to a common graphics file is welcome to repost it).
It incorporates a delay circuit so that when the engine is switched back to diesel the return line remains set to VO for a user definable period of time (see schematic).
The parts should cost $10 or less, and to build it you'll need to have basic soldering skills and the ability to follow a (very) simple schematic.
I offer this circuit freely for personal use and with no warranty, if you choose to use it I take no responsibility for any problems or damages that may occur. No one may sell this design or make any profit from it except me.
On paper it looks fine, but I have not even benchtested it much less tested it in an application.
Do not substitute TTL logic for the CMOS, I specifically used CMOS to avoid needing a voltage regulator and to cut down on cost and parts count. The values I used for components *seem* right to me, but I put this together in around an hour so I might have kludged the math a touch or something. I used components with wide tolerances, though.
I chose parts which are very commonly available, cheap, and reliable. No MCU unit, just straight logic chips (so no programming). If you have trouble finding the LMC555 you can replace it with a TLC555 with no circuit changes. The venerable old LM555 *might* work, but we are getting into iffy territory.
This circuit is easily modifiable to handle other chores (alarms, purge alert, VO or diesel indicators, etc.). You'll have to set the timing of the return valve yourself. In the circuit it is set to about 16 seconds but you'll want to time how long it takes your vehicle to purge the VO from the fuel lines and set up the circuit based on your own car (simple to do).
If enough people express interest I might be willing to add features and benchtest the design. I don't see a point right now since I don't know if anyone is at all interested.
Anyways, I really enjoy learning from what I read at this forum and hopefully someone can use this contribution.

EDIT:

Old version of circuit deleted.

This message has been edited. Last edited by: SethK,

Hi, I figured out how to export a .BMP image from another one of the CAD systems I use.

Some notes:

Tie all unused inputs on IC2 and IC3 to positive (these are pins: 5, 6, 8, 9, 12 and 13), also tie pin 14 of both of them to positive. Pin 7 of IC2 and IC3 go to ground. The capacitor between pins 8 and 1 of IC1 should be as close to the pins as possible (I usually just straddle the chip with the capacitor). All capacitors should have a minimum voltage rating of 25V (anything higher is fine). Only C1 should be polarized, pay attention to where + and - go. C3 isn't strictly necessary since our supply is well regulated, but to make the system more robust and reduce timing errors I included it.

****I made some changes to the original design and ran it through error checking and found I had missed a ground, so be sure to use this version instead of the original (sorry).****

S1 is your WVO/Diesel switch, when S1 is on (sending power to this circuit) and the temp sensor is high enough, WVO turns on. Pin 1 from IC3 comes from whatever temp sensor you use, the sensor has to supply about 5V to turn on the WVO and switch from Diesel(up to 15V, so it can supply straight from the battery). You need to check how much current your solenoid valves draw, the relays I use in the schematic (K1 and K4) are rated to handle up to 2A continuous and bursts of up to 5A (for one second). K1 connects to your send solenoid and K4 connects to your return solenoid. Both solenoids must be set up so when the solenoid is activated they turn on the lines to the WVO. If you change relays from what I specified either stick with solid state or learn about freewheeling diodes.

To control how long the return lines stay in the WVO position after the send line switches to diesel, use this formula: 1.1 * R * C and change R1 and C1 to the values you decide on. With the circuit as is the timer will run for about 16 seconds.

The circuit will draw minimal power, but if you're concerned about drain while the car is off connect all the power lines into an ignition switched fuse.

I think that is everything, but if you have any questions feel free to ask. If anyone cares why/how the circuit works, I'd be glad to explain it.

EDIT:

Old version of circuit deleted.

Hi Seth,
An automated controller seems like a good idea... It seems like it would work with just about any VO systems not just a Fattywagons system.. While it may seem like a rater simple circuit to you, it may be beyond some DYIers to make it themselves.. If you ever have any interest in selling a complete product I may be interested on putting it on the webiste.. Why don't you make a couple of these, test them and let folks on the forum know how they work...

Some have used turbo timers to make things semiautomatic.

Hi Seth,
It has been toooooooooo mannnny years since I have done any electronics, therefore with your permission I was going to give the schematic to a friend of mine who is in electronics and have him build one for me.

Hi Seth,
That was generous of you to share a circuit.
First, let me state what I think it does:
The driver manually flips a switch to veggie mode. Then, when the temp sender sends 5v, the first solenoid switches to veggie. 16 seconds later the second solenoid for the return switches to veggie. Then, when you want to shut down or purge, you flip the switch back to diesel, and 16 seconds later the return solenoid switches the return to the diesel tank.

THoughts:
I like to have control of exactly when I switch to veggie, so I would want the temp sender control out of the circuit and have it instantly switch to veggie when I flip the switch. So I'm guessing that IC3 would be eliminated in that case?
Also, being a little wary of the circuit functioning correctly, I would want LEDs on the switch leg for each solenoid valve, so that I could see when power was or was not being sent to supply and return valves. I guess those could just tie into K1 and K4, right?
I am a bit tired of counting, so I am thinking it would be fun to try this this summer.

Thanks again for sharing.

Hi Pizzaman, the schematic and design is completely free for personal use. You can use it as is, modify it, or whatever.

FattyWagonMan, I stated your system because I noted that some of your schematics have true returns and not just looped returns, this is essential for this circuit to be useful. Yes, though, this will work with any system using true return lines to both diesel and WVO.

Soyburban, very close!! Notice the Q1 transistor, this ensures that when the switch is turned on (WVO on) the timer is disabled (it offers a cleaner path to ground than to the timer). So when you first turn on the switch and the temp sensor is high enough the system turns on the WVO send and return. When the switch is turned off the supply to the base of the transistor is cut off and the transistor turns off, thereby turning on the LMC555 timer circuit. The 555 holds the return valve on WVO for the time you set with R1 and C1, then allows the return to switch to diesel. The major purpose is to keep WVO out of your diesel tank, but it was easy to add in the delay in turning on the WVO until it was hot enough, so I just tossed it in.

Yes, to add indicators you add LEDs into the relay circuits (on the control side of the relay, so it is electrically seperated from the valve), but add a resistor in series with the LED to limit the current. Most common LEDs work well with around 15mA or so (up to about 20mA), so you could use a resistor somewhere around 330 ohms. I get about 100mW at 5V and 20mA, so a regular 1/4 watt resistor should be just fine. If you want to add a purging indicator you can put an LED and resistor between the #3 pin of the LMC555 and the OR gate (thats all IC2 is, we are using one OR gate in a chip that holds 4. IC3 is just an AND gate) it is going to.

As to making some for sale, I hadn't really considered it. If I did that I would want to switch to 7400 TTL logic and use a voltage regulator just so I can be much more precise with the math. Right now we are well within the tolerances, but since we don't have a perfectly regulated voltage source I don't know exactly where in the tolerances we are.
Unfortunately that would add costs and instead of a $10 controller board people would have a $50 controller board.
Right now I am developing an LCD display system for WVO (showing what fuel you are using, whether you are purging and how long the purging cycle has to go, possibly fuel temp and levels, etc.), and thats whats interesting me right now. It should be adaptable to virtually any system, but I was primarily aiming this as an accessory to the FryBrid system because it has so much information it can output. Hopefully I will be able to do that in my free time over the summer, but I'll take an afternoon and testbed the controller board above and report back any issues or changes.

Thanks for the feedback!

Seth,
For the sake of working my brain past it's capacity, I tried to figure out what you said.
I think I get it but it's been a long time since high school electronics class.
Anyway, what I think I would want for my application is delayed switching each way. The delay is about 45 seconds for my soyburban.
So... If I delete IC3, tie pin 2 of S1 to pin3 of K1, and add a delayed ON timer (there is one, right?) and tie pin 2 of S1 also to the trigger for delayed on, and tie the output of the timer to pin 1 of your OR gate, IC2. Then I think i'd ahve delayed switching for on and off and keep things in their proper tanks. Is there a delay timer that would work for that purpose?

Thanks!

Soyburban, let me put this in order in my mind so I am sure I am answering you correctly. I believe what you want is this:

On startup:

1. Turn on switch and send line switches to WVO once temp is high enough.

2. After specified time (after purge of diesel from system) return line switches to WVO. Now all systems are switched to WVO.

When ready to shut down:

3. Turn switch off and send switches to diesel.

4. After specified amount of time (after purge of WVO) return switches to diesel. Now all systems are switched to diesel.

Is this correct?

In the above circuit IC3 is controlling point #4 above and point #2 is ignored (I figured a little diesel in the WVO tank wasn't as much of a problem as having some WVO in the diesel tank).

Hopefully I understood you correctly, I am posting a modified circuit to do what is outlined above.

Notes: IC1A and IC1B are not seperate chips, it is a 556 duel timer (has two 555 timers in one package).

IC2A and IC2B are also on a single chip, it is the 4071 chip which contains four logical OR gates.

Now above I said to tie pins 5 and 6 of IC2 to power but you'll see in this schematic that those pins are now used as part of the circuit, so don't tie them to power.

R5 and C5 control the time it takes for point #2 above to happen (IE the delay before the return line switches to WVO right after turning on the switch).

With the current values it will wait about 9 seconds. To change this just change R5 and C5 using this formula 1.1 * R5 * C5.

Edit: I made a slight change to make timing easier for DIYers, if you look at R5 it has a value of 8.2K ohms (8200 ohms) and the timing is about 9 seconds.

Also, if you look at R1 you'll see that it has a value of 15K ohms (15,000 ohms) and the timing is about 16.5 seconds.

So if you want a timing of, for instance, about 18 seconds in one of the timers just use a resistor just a little under 18K ohms. This way you don't have to worry about the math.

EDIT:

Old version of circuit deleted.

Good morning Seth,

quote:

Originally posted by SethK:
Soyburban, let me put this in order in my mind so I am sure I am answering you correctly. I believe what you want is this:

bOn startup:

1. Turn on switch and send line switches to WVO once temp is high enough.

2. After specified time (after purge of diesel from system) return line switches to WVO. Now all systems are switched to WVO.

When ready to shut down:

3. Turn switch off and send switches to diesel.

4. After specified amount of time (after purge of WVO) return switches to diesel. Now all systems are switched to diesel.

Is this correct?

Yes!... except I will not use the temp sender and and gate IC3, I will just switch when my temp is warm enough according to my gage, but leaving it in makes sense, people can either use it or not.
I am excited about making this.
The reason I want the delay both ways is on my system it is more like 45 seconds from supply T to return T, so I don't want to send diesel into the veg tank for that long, time after time.
I may not be understanding your new circuit correctly (very likely) but I'm not sure why the second timer is tied into the control relay K1 for the supply fuel.
Seems like the supply solenoid is pretty much driven by S1 (and temp sender if used), either on or off immediately upon switching, the delay occurs with K4, the return solenoid.
Am I misunderstanding the schematic?
Thanks!

You are indeed reading the schematic correctly, and you totally caught my error (apparently I shouldn't be designing stuff right when I wake up)!

I should have all the parts in my workshop, so let me testbed the system and make any other corrections before you invest in building it.

I should have time this weekend to do that barring any major issues.

See also:

http://www.vocontrol.com/forum/viewtopic.php?t=9

Hi Ray, looks like a very nice system!

Ok Soyburban, I redesigned the circuit to behave per your specs. I benchtested it and found no problems.

I decided to add in a voltage regulator, it should only raise the cost by a dollar at most.

When your system is hot enough, turn on S1. This will immediately activate K2 (the send valve relay) and after about 45 seconds K1 will activate (return valve).

When you are almost home turn off S1 and press S3 (get a normally open, momentary button). This deactivate K2 (switching to diesel send) and will keep activated K1 (keeping return on WVO) for about 45 seconds for the purging cycle.

S2 is a bypass switch in case you make a short stop. Just leave S1 set to WVO and when you get back in the car flip on S2 for a minute so the return valve doesn't get turned to diesel for 45 seconds. Or if you want you can just press the purge button when you get back in the car (with S1 still on) and it will hold the return valve to WVO.

If you ever want to modify this so that it automatically switches when your engine is hot enough, just get a thermostat which closes a circuit at the temp you want. Then connect it between S1 and the OUTPUT terminal on the 7805 voltage regulator.

Oh yeah, LED1 is the indicator that your return line is switched to WVO. LED2 is the indicator that your send line is switched to WVO.

Let me know if anything is unclear.

EDIT:

This circuit, a complete parts list and some related notes are posted on my webpage at:

http://people.emich.edu/skoster/WVO1.html

EDIT:

Old version of circuit deleted.

Excellent, Seth. I'm off to Radio Shack on Monday!
So, I had a couple questions. First, I think there is a switch that will do momentary on, off, and continuous on. This would eliminate the push button. When purging, you could just press all the way down on the switch, for momentary on, then release which would be off.
I guess that was a suggestion, not a question. That switch would probably cost more than a push button and a SPST, though.
Next, the question: Does the trigger for the IC2 timer need to be momentary? If not, it could be an on/off/on switch, or equilivant, with the second on tied to ground, like S3.
Ansd lastly, if you have this circuit tied to a power source that is not run through the ignition, then you could eliminate the need for S2. Would there be much power draw on this circuit with S1 open (overnight mode)?
Thanks again for sharing this, I think it is a nice upgrade from the manual count and switch.

Yes, a DPDT switch with either a momentary or non-momentary second on would work. IC2 will time out even if the trigger is held closed, but I prefered the momentary switch because I didn't want people accidentally leaving it on when they turned off their car and started back up in the morning.

With S1 open the circuit itself draws minimal power, under 10mA. With S1 closed your power draw is significant, though, depending on the draw of the solenoids you use. For instance if your solenoids draw 5 amps and both are activated you will be using 60 watts (P=E*I).

If you remove S2 also remove it's associated diode D4. Also, I used a very safe value for R2 and R3 (the resistors limiting current to the LEDs) because of concerns with voltage doubling if S2 and IC1 are both activated, and they might not be very bright. So you can change those based on what your LEDs can handle. Just figure out what current your LEDs operate best at and determine resistance with R=E/I (E=voltage, I=current).

I made a slight change to the circuit because I don't know what relays you'll be using so I decided to seperate it from the control of IC1.

Hi Seth,
Thanks for making / sharing the design...
I'll put up a link on the Fattywagons WS ...
Does DYI automatic controler sounds OK?

Sure, thanks for the link! Also, I went ahead and streamlined it a little more and got rid of 2 diodes so as to bring the parts count a little lower. I think I have it about as minimal as possible at this point. Here is the newest circuit.

As I was testing the latest circuit I noticed an unintended feature. If the purge cycle runs while S1 is closed LED1 will get about twice as bright.

This circuit, a complete parts list and some related notes are posted on my webpage at:

http://people.emich.edu/skoster/WVO1.html

WVO3.JPG (76 Kb, 27 downloads)