Electronics 2000

Hi to all, I have some 15 years in electronics fault finding and have a thriving laptop/PC repair business, I received a phone call today which got me thinking, this chap who must own a petrol station asked me if there was any way that he could install circuitry within the pump that would deliver a set amount of fuel, £5, £10 and then cut off, I thought "hmm", it would need to go between the pump trigger and the digital display, or between the auto cut off and the digital display, the auto cut off is regulated by a valve within the pump handle so thats not an option, it must also have a reset attached to the sensor contained in the switch when you replace the pump, although it seems quite complicated I actually think it can be very simple, I just need a schematic for a relay attached to a counter which in turn connects to the digital display, also something that wont cause the fuel to ignite "Dr Evil laugh!!!", so to sum it up...

Circuit which connects to the digital display of the fuel pump.

Set to £5, £10, £20, £30 etc

Cut off relay

reset switch

(There is a slight possibility that the existing circuitry may have an option to incorporate some form of metering system, but what I know about fuel pump circuitry you could write on your little finger nail with a black marker)

I am new to this forum and am unsure whether I will receive replies to my email address, if I dont then my email address is cover-it@hotmail.co.uk.

Any suggestions would be greatly appreciated, unfortunately my local Tesco filling station already has this incorporated into its pumps, so nobody will be getting rich off the patent, but we might have some fun along the way, Kind regards, Andy Meeks, Northern Ireland.

I can only talk of the theoretical side of things, if you blow up a petrol station with additional electronics then your insurance company will not be too happy!

Firstly you need to figure out what sort of signals you have which drive the display. I recently asked on another thread about using a 7 seg display but came unstuck when I discovered the unit was a bespoke display which just had power and data lines. (albeit my CD player was not quite as dangerous as a petrol pump!!)

The easiest type of signals to deal with are BCD (binary coded decimal). If you have these it is pretty simple to design something that compares a BCD signal to a preset BCD signal from thumb wheels etc, giving an output when the two signals match.
The only issue there is getting an output act quickly enough to stop dead, I know when I fill up my car stopping dead on the correct penny is now nigh on impossible - the darn things sometimes go up in 2p stages!

Hi Paul, there is also that problem of the dreaded 1p or 2p over fill :-p, I will be honest and say that this is uncharted territory for me, I advertise my services regarding laptop/PC repair and I get this call about fuel pumps, but I cant turn away from a challenge, I have emailed the guy and asked for any serial/model numbers of his existing pumps to check the schematics of the pumps circuitry, all I know at this stage is that he has 3 fuel pumps and that they are digital display, I will be in touch when I know more detail, thanks for the reply

P.S, good point regarding insurance companies by the way

To sastify the insurance companies any parts you use must be proved 'intrinsically safe'.Basically it means that the parts have been tested and proven to not spark or arc in volatile situations like petrol vapour hanging about.

This means anything you use from simple relays to microproccessor controls.You will have to get any parts from an approved 'intrinsically safe' manufacturer someone like MTL Instruments who supply electronics to oil wells etc. Who also might be able to advise you on your plan?
The downside of course is you might pay a small fortune for a relatively simple device like a relay.

The conversation so far...,
"Hi Andy

I need a payment system to work with 3 forecourt pumps

1) Insert money in payment meter (coin and note ) and the total should show up on a display.

2) A way of choosing which pump ,1 2 or 3

3) Lift pump handle and dispence fuel to the same amount on meter (i was thinking as the pump meter goes up the payment meter goes down) and the pump won't reset itself if there is credit on meter

4) Pump will automatically stop when credit is used

5) Pump will reset itself when next user lifts it. and so on

pumps are old but they have a digital read out

Andy you probably will figure out a better way of doing this and any advice or ideas is welcome,
i can build housing for the payment meter and supply coin and note acceptors .

If you need anything you have my number and email ,look forward to see what you come up with,

thanks Chris"

"Hi Chris, thats a big task my friend, I have already began the process of sourcing schematics etc, I will have to tackle this one stage at a time rather than shoving the entire cake in my mouth at once lol, the reset will be via the switch that activates to turn the pump off when the pump handle is replaced into the housing, the extra circuitry will be attached to the "amount in £ on the digital display", whether I/we can incorporate a relay into/onto the existing circuitry is unsure, can you send me any model numbers, serial numbers off the pumps you have?, that would be a start, I could examine the existing circuitry to see if there is room for modification, I know that my local "Bangor, bloomfield shopping center" Tesco garage has this facility, once we have figured out the relay to set the amount, the rest should be easy enough, this is uncharted territory for me but I relish a challenge, andy.

P.S, Hiring a school leaver for £10 per day to sit at the pumps and take money and fill vehicles to the desired amount might be an easier option..., I am just kidding :-p, if you could send me any serial/model numbers off the pumps that would be a great start. "

"Hi Andy ,the pumps I have are pumptronics series 100 single pump. The pumps are not in place at the moment and they will have to be passed by weights and measures before the are in use .
and will have to have an electric certificate .
chris"

"Hi Chris, there are systems you can get for as little as £12.50 per month, these connect straight into your current EPOS (Electronic point of sale) system, ( http://www.headstartglobal.com/download ... nience.pdf ) , I have searched for the make and model of pump you have, there is circuitry you can buy, unfortunately they are for dozens of pump manufacturers except Pumptronics, ( http://www.deliveryproducts.com/fuel_pu ... oller.html ) , but I wont be deterred, is your reason behind an OPT (Outside payment terminal) to cater for commercial truckers?, the reason I ask this is that there is systems that cater for commercial truckers via chip and pin cards, sorry for asking all these questions but I need to be clear in my mind when I am searching for a suitable system that is both simple yet serves your requirements without unnecessary functionality, like an integrated doughnut sugar sprinkler "A bit of humor ", I will get back to once I have sourced a suitable workable schematic diagram, or an existing low cost alternative, Andy."

"Hi Andy , all i need is to link into the £ sign display on the pump with the meter £ sign display and to get the two of them working simultanously in opposite directions and when the meter credit is at zero (just like a electric meter timer box) it will cut of power to the pump is there anything you know of that could do this . all the rest can be added at any time . All i want is something simple display to display in opposite directions . your thinking alot bigger all im thinking is a small money opperated meter . it probably was my fault listing everything i need it to do at the start ."

"Hi Chris, unfortunately there is nothing simple about what you are trying to do, in essence what you are trying to do is integrate a separate electronic circuit into existing and unknown electronic circuitry, yes you know what the existing circuitry does but not how to tap into its basic core functions, which I/C controls the £?, you can trace the tracks back to an I/C but it may have 80+ points of entry/exit, this is why I needed the model/serial number as there may well be an adapter/connector that integrates the functions you are trying to get, manufacturers often make "one board" which has optional extras, in essence it sounds simple until you open the cover of the pump and expose the circuitry, where do you begin?, it would be too simple to just solder two wires from the £ digital display of the pump, but the display is just an electrical digital output which comes from an I/C, it may well be simple but it seems its uncharted territory for the both of us, it may well be as simple as soldering two wires from the digital display, connect them to a separate countdown timer which sets a given amount and then cuts off, but at this stage in the development its fondling in the dark i'm afraid, wait until I can find a schematic diagram or someone who is familiar with such systems, I am a member of various electronics forums and currently have several heads working together, Andy."

"Just a thought "thinking aloud", you already have the payment meters with digital display right?, to somehow link the readout from the coin meter to the readout of the pump.., the problem is that there is nothing within the circuitry of the pump that has an auto stop function at any specific increment on the display, £5, £10 etc, so we need a circuit that can read the display of the pump and link it to the countdown display of the meter, let me run that past a few people.., sorry for all the emails, what we really needed was a brainstorming session where we could take notes and analyze available circuitry, but the core of what you are looking in simple terms is ( a circuit that can read the display of the pump and link it to the countdown display of the meter)."

That's the entire conversation via email, I am starting to think that its an impossible task, I realize with electronics nothing is impossible, but coupled with fuel vapors and electrical sparks from relays, hmm..., any help would be appreciated and recognition given, Andy.

Hi, I just stumbled upon this..., http://www.edutek.ltd.uk/CBricks_Pages/Counter_BCD.html , Andy.

It's got to be an off the shelf system fitted by someone with more degrees and paper work than Mick Faraday... or you will get the jail.

Tar&stuff.

Hi to all, Been some progress, it is a BCD board, I have included 4 pictures that were sent to me and will include the accompanying email...

"Hi Andy ,i think we are on the right track there is a dual bcd on the display (motorola MC14514BCP) just googled the code which is attached to the display if you want i can send you the display in the post so you can have a better look at it ? . I have not got a payment meter as yet i was wanting to get this part sorted first"

I couldnt send all the pictures as there is an upload limit, so here is the most relevant picture..., jeeeze louise, it wouldnt even let me send one picture , "think Andy think ", I cant find a url for the circuit board and must ask if anyone thinks they may be able to help could you send me your email address's, all of which will remain anonymous, or I am on Facebook "https://www.facebook.com/BangorLaptopRepair" and I can send the pictures via Facebook, I appreciate any help and any help will be recognised , Andy.