Discuss Veg oil system control design help. in the Auto Electrician Forum area at ElectriciansForums.net

Welcome to ElectriciansForums.net - The American Electrical Advice Forum
Head straight to the main forums to chat by click here:   American Electrical Advice Forum

W

Wheresthedog

hi all

I'm working on a veg oil conversion for our (1997) 110 defender and have some ideas of how I'd like to control it but my auto electric knowledge is poor and I was wondering if anyone could help? I've contacted a few auto electricians and no one wants the job.

I have bought a stack pro water temp gauge which can be programmed to act as a switch once a certain temp is reached:

52mm Auxiliary Gauges: Pro-Control - http://www.stackltd.com/instruments_pro_control.html


And an on (veg) / off (diesel) / on (purge) 'master' carling switch:

Veg oil system control design help. {filename} | ElectriciansForums.net




The plan is to start on diesel and once the water (engine) temp gauge reaches 70c the engine switches to veg oil.

A minute or so before the journey's end we will switch to 'purge' and diesel will be drawn from the diesel tank but the unused fuel will be returned to veg tank to clear the lines of veg oil ready for the next start up.

He's a schematic of the system:

Veg oil system control design help. {filename} | ElectriciansForums.net



There are 3 x 3 way solenoid valves and a 12v diesel pump (veg oil is pumped via a mechanical pump and will always be in operation).

On / Veg mode: 1, 2 and 3 and diesel pump is powered = veg oil drawn from and returned to veg tank in its own loop and diesel is drawn from diesel tank and used to run vehicle. Once stack pro water temp gauge reaches 70c: 1, 2 and 3 and diesel pump become unpowered = veg oil drawn from and returned to veg oil tank (engine now running on veg oil).

Off / Diesel mode: 1, 2 and 3 and diesel pump are powered = diesel drawn from and returned to diesel tank.

Purge mode: 1 and 2 are powered, 3 is unpowered = diesel is drawn from diesel tank and returned to veg tank.
Although diesel mode is activated in the carling switch off position the solenoid will be powered as the vehicle will be in veg mode most of the time and will use less battery power this way.

I'm not sure what I need to make this system work (relays? Diodes? Etc) or indeed if there are any problems/impossibilities with what I've proposed?

Any help and advice would be much appreciated. (12 volt planet said they can help with all the parts but can't help with the design).

Cheers
 
Unfortunately @Wheresthedog your images don't appeared to have worked, and I'm not clear what 1, 2 and 3 are? Solenoid valves?

My gut feeling is a combination of diodes and relays, but more than that is difficult as some of your explanation doesn't quite make sense. On/Veg mode: 1, 2 and 3 and diesel pump powered, Off/Diesel mode: 1, 2 and 3 and diesel pump are powered. Which is it, or would it be clear with the pictures?
 
Would it not be a lot easier to get a converter for veg oil and then put that in your tank?
 
but more than that is difficult as some of your explanation doesn't quite make sense. On/Veg mode: 1, 2 and 3 and diesel pump powered, Off/Diesel mode: 1, 2 and 3 and diesel pump are powered. Which is it, or would it be clear with the pictures?

You need to read it all :)

"Once stack pro water temp gauge reaches 70c: 1, 2 and 3 and diesel pump become unpowered = veg oil drawn from and returned to veg oil tank (engine now running on veg oil)"
 
Hi,let us assume you are direct debiting the duty ;)

Do you have two separate tanks? If so,you will have to set up a method of diverting the fuel return lines,or you will get over spill and dilution!

The main problem with these kits,is if you stand behind while the engine is running,you feel like ordering a steak and kidney pudding:)

Hang on,just seen solenoid 3...fair bit of pipework,then.

Nope...second edit...i stand by my initial comment. Unless there is some space-age sampling and ECU,you will get,at least dilution,or mixing,due to change over from one fuel to the other,will return,the remnants of the previous fuel supply, to the other tank.
 
Last edited:
Yes two tanks (see schematic above). The system works well - there can be no overspill in this setup. Need help with the electrics only.
 
Nope...second edit...i stand by my initial comment. Unless there is some space-age sampling and ECU,you will get,at least dilution,or mixing,due to change over from one fuel to the other,will return,the remnants of the previous fuel supply, to the other tank.
It doesn't matter that there's dilution or mixing of the veg oil. It only matters that the diesel tank doesn't receive any veg oil. The diesel only serves to start the engine from cold.
 
Last edited by a moderator:
Hi,but if solenoid 3 is a 3 port diverter,as i suspect,every time it switches over to chip-fat,the remaining diesel in the lines and injection pump,will be returned to your oil tank.Every time.

I have set these systems up,in the heady days of rebated fuel confusion,where we attempted to arrange plant and vehicles,so site use was on red,and road use reverted back to derv.

It was cat and mouse with a Previous version of VOSA,and the cost savings were not enough to run the gauntlet;)

VOSA,incidentally,are who may be sticking their sampling tube in your ride,on smelling a fish supper!
 
I came here for electrical advice.

There's no duty on veg oil as a fuel - Veg Oil Motoring, diesel engine conversions to run on vegetable oil » Legality and Fuel - http://www.vegoilmotoring.com/eng/legal-stuff

I can't put it any more plainly than it doesn't matter that diesel will go into the veg oil tank. That's exactly what purge mode is for - to rid the lines of veg oil and fill with diesel 1 minute of so from journey's end so the car is ready for the next cold start.

I've had 3 people respond now - 1st didn't read my original post properly and you're offering useless and false advice.

Anyone willing to help with the electrics?
 
I apologise if i have offended you,but regarding your "purge",you are incorrect.

As for your request for electrical help,i can assist.

I would change out your short fuse,for one with a higher value.

Good luck.
 
I've had 3 people respond now - 1st didn't read my original post properly and you're offering useless and false advice.

Anyone willing to help with the electrics?

Granted I didn't read it all, but it was lacking pictures (I like pictures) and I wasn't clear on what you were trying to achieve. It was late and I'd been working all day so instead of cooking up a half baked answer I did the sensible thing and went to bed with the intention of having a think about this morning.

I would second the advice from @PEG . You've been thinking about this for some time, if you want decent answers, you're going to have to put up with people asking (what may to you be) silly questions or highlighting what they may see as potential flaws (especially if they have past experience).

This is my sketchy answer to your enquiry. I've looked at it several times and I think it will fit what you want (to paraphase the Febreze adverts... SparkyChick has become schematic blind ;) ). It may not be the best or most optimal in terms of component counts etc. The fact the switch doesn't have a middle on position adds a relay in my solution. I would drive each item through it's own suitably rated relay with individual fuses, and some overall protection for the stuff in between. Most of this could be built on Veroboard depending on the coil specs for the relays. I would use automotive relays for the output drivers, you can get fairly decent relay mounts for simple relays quite easily.

This is a very simplistic approach, there is no fail safe in this at all. If one output circuit fails, you may not know until veg oil is squirting out your diesel tank filler. A much better solution might be to implement using a microcontroller such as an Arduino... then you may be able to do crazy stuff like detect that you've turned your ignition off without purging and it will keep it running and warn you, or maybe even add pressure sensors to detect solenoid failure. Just a thought.

Anyhow, good luck with your endeavours.

View attachment 35695
 
Gosh - thanks so much for your effort! That's cheered me up no end :) I'll pour over it later on and get to grips with what you've suggeted.

Much appreciated!!
 
In essence the diodes form four logical or gates that combine the inputs from the switch to drive the outputs as required. I've added protection diodes to the relay coils to prevent damage from the high voltages caused as the field collapses (there is a technical term for it which escapes me at this moment). You may want to add a similar diode to the relay driven by the Stack gauge, but I suspect (they look well engineered) they may already incorporate it.

The relay at the left that is used to generate the 'D' drive line... if you can get a switch that is three position on-on-on (single pole triple throw), you could do away with that.. it's only purpose is to generate that line. Looking at those switches, I'd be very surprised if you couldn't and maybe swap the switch top over.

In terms of component numbers, the protection diodes, I typically use something like an IN4001. I suspect these would be fine for the logic diodes as well, but depending on the output relay coil specifications, you may need to use something else with a higher forward current rating.
 
That's something I hadn't thought of - failsafes! The Arduino looks amazing but far beyond my capabilities.

I wonder if I could include an LED after each component (solendoids and pump). That would tell me if power was getting to each component at least right?
 
That's something I hadn't thought of - failsafes! The Arduino looks amazing but far beyond my capabilities.

I wonder if I could include an LED after each component (solendoids and pump). That would tell me if power was getting to each component at least right?

So I was looking at the schematic I sketched out, yes you could add an LED to indicate output status, but that relies on you knowing what status each one should be in for a given mode.

If you were to use some good old 4000 series CMOS logic, you could have the system work out if there is a fault (either power present when it probably shouldn't be or when there is no power going out to the solenoid/pump) by using XOR gates. Please note, these must be CMOS devices and they must be capable of 15v operation. You cannot use TTL devices without implementing a power supply and input signal level translation as TTL expects 5v typically and sticking 12v on their inputs is likely to make them go off with a bang. In case you're not familiar with logic like this, 0v = false and around 11-15v = true, which makes this family suitable for use with automotive electricals (assuming it's 12v).

The schematic below is a rough idea. I think I've got all the logic right, but as with the first, it's all too easy for your brain to fill in the missing bits or magically correct your mistakes.

U1 - Quad 2 input XOR gate
U3 - Quad 2 input NOR gate
U4 - Quad 2 input AND gate
U5 - Triple 3 input OR gate
T1 and T2 are fairly high power NPN power transistors. The exact model would be governed by the current required for the relay coils.
T3-T6 - Low power NPN transistors (something like a BC108 should suffice as it's only going to be switching an LED)
D5 and D6 - 1N4001 diodes to protect the switching transistors
F1-F4 - Fuses appropriate to the current requirements of the devices being driven
R1-R4 - Roughly calculated as 625ohm (assumed 0.5v forward voltage drop across the LED and a maximum forward current of 20mA)
RE1-RE4 - Output drive relays. Exact specification will depend largely on the devices

DRIVE12P (which will trigger the output drive for solenoids 1 and 2 and the pump) uses this logic - DRIVE12P = (VEG and (NOT TEMP)) OR (VEG NOR PURGE) OR (PURGE)

DRIVE3 uses this logic - DRIVE3 = (VEG AND (NOT TEMP)) OR (VEG NOR PURGE)

The fault indicators, take a feedback from the outputs SOL1DRIVE, SOL2DRIVE, SOL3DRIVE and PUMPDRIVE and XOR them against DRIVE12P, DRIVE12P, DRIVE3 and DRIVE12P respectively. If both are off or on, then the output for the fail will be 0, but if they are different then the output will be 1 and the LED connected to the relevant fail line will be on. This provides a basic electrical fail indication which is capable of detecting a relay failure or a fuse failure. Any more than that would require processing power to monitor current consumption at the output to detect overload (fault) or no current flow (wiring/component failure).

In a minimalist solution you only need two output relays. You can still use the logic to detect fuse failure for each of the outputs, you'd just scrap RE2 and RE4 and link their two fuses to the output of RE1, however loading may be a problem depending on the diesel pump rating.

Forgot to add these to the schematic... you will need pull down resistors (about 10kOhms) between 0v and the inputs VEG, PURGE and TEMP and also on the outputs after the fuse for SOL1DRIVE, SOL2DRIVE, SOL3DRIVE and PUMPDRIVE. These will stop these signals floating. I would also addprotection diodes on the outputs SOL1DRIVE, SOL2DRIVE, SOL3DRIVE and PUMPDRIVE to prevent the field collapse in the coils/windings frying the chips. It may also be prudent to add a fairly chunky electrolytic cap across the supply to provide a little bit of smoothing and 100nF decoupling capacitor across the supply to each chip.

Enjoy.

View attachment 35712
 

Reply to Veg oil system control design help. in the Auto Electrician Forum area at ElectriciansForums.net

OFFICIAL SPONSORS

Electrical Goods - Electrical Tools - Brand Names Electrician Courses Green Electrical Goods PCB Way Electrical Goods - Electrical Tools - Brand Names Pushfit Wire Connectors Electric Underfloor Heating Electrician Courses
These Official Forum Sponsors May Provide Discounts to Regular Forum Members - If you would like to sponsor us then CLICK HERE and post a thread with who you are, and we'll send you some stats etc
This website was designed, optimised and is hosted by Untold Media. Operating under the name Untold Media since 2001.
Back
Top
AdBlock Detected

We get it, advertisements are annoying!

Sure, ad-blocking software does a great job at blocking ads, but it also blocks useful features of our website. For the best site experience please disable your AdBlocker.

I've Disabled AdBlock