Timed drink dispense

Thread Starter

GuitarDemon

Joined Oct 16, 2019
4
Please could I have some advice on the components I need to run a drink dispense motor for a specific amount of time? All I need it to do is from a press of a button, I would like to drive 6 x 12V pumps to dispense spirits in 22ml shots. I've been advised by the pump manufacturer that the most accurate way to get this measure is to drive the pumps for a specific amount of time (2.7 seconds), but the timer would need to be accurately adjustable (in milliseconds ideally). I am a mechanical engineer, but have some electrical knowledge, but not to this level! Any help you could let me have, or point me in the right direction, would be greatly appreciated!
 

DickCappels

Joined Aug 21, 2008
6,388
You might be able to find a precision adjustable timer to your liking on Amazon.com, eBay.com, or alliexpress.com.

Other promising approaches are to use an inexpensive microcomputer -basically a single chip on a board, but it would need to be programmed in a C-like programming language, assembler language or other method, or to make analog or digital timer circuits that can be adjusted with dip switches or a screwdriver.

I suspect looking for a pre-made adjustable timer would be your best bet starting out.

Which way would you like to go?
 

Thread Starter

GuitarDemon

Joined Oct 16, 2019
4
Thank you for the reply! I've seen an adjustable timer relay on the RS website, but I need help as to how they connect. It looks straight forward, I think I need a 12V transformer, a push switch to active the system, and the timer. All 6 pumps will need 7.2 amps when running. If you know of a wiring diagram (dumbed down for me!) that would show me anything else I need, and how to connect them, I would be really grateful!
 

Tonyr1084

Joined Sep 24, 2015
4,539
Welcome to AAC

Just to be the voice of trouble, there are other things to be considered when dispensing a liquid. Pressure, flow rate and time. Also, you're going to want it to be consistent. Changes in temperature can have an affect on electronic circuits as well as motor speed and fluidic pressures. Pressure is in relation to ambient pressure, which changes daily. Hourly. Can even change in a matter of minutes (when warm or cold fronts pass through).

The size of the tube dispensing the fluid is a part of the equation as well as the speed of the pump motor, how quick it comes up to speed, and a regulated pressure at which the fluid is pushed through the tube(s). To run six pumps at once? Perhaps it would be better if you maintained an air pressure and use that to push the fluid out, using an electronic valve.

I've never messed with a fluid dispenser. Depending on level of accuracy you're going to have to decide on which method is better. Coffee dispensers generally use water line pressure to dispense water into the brewer and use a metered pump (a piston of given dimensions and travel) to force the brew through the filter into the cup. Simply running a pump of unspecified type - be it a centrifugal impeller or a diaphragm type all make a difference in what you're doing and at what level of accuracy you desire. Positive displacement pumps can be more accurate. I'm just not sure of the level of accuracy you desire. You mentioned 22 mL, but how accurate do you want that?

Well, hopefully I've tossed out enough for you to consider. More information will help us determine what may be the best way to go. Or perhaps we can suggest an alternative approach. There's tons of talent here. Far beyond what I may be able to provide. As I opened, I can be the voice of trouble. I can easily be the monkey with a wrench.
 

BobTPH

Joined Jun 5, 2013
2,392
22 ml in 2.7 seconds needs a 12V 7.5A motor? I can’t say I have any experience in dispensing liquids with a pump, but that sounds way over powered to me.

Bob
 

Thread Starter

GuitarDemon

Joined Oct 16, 2019
4
Hi Tony, thank you for the reply. The pump manufacturer has tested the pump and dispensed the liquid accurately using a home-made timer. He's managed to dispense 22ml with a 1ml tolerance, which is acceptable. I just need a durable timer (the RS Pro EZM-3735 is the one I'm looking at) for this commercial application. I'm also struggling to find a 240V ac to 12V dc transformer, which the pumps use. All the ones I can see on RS are 12V ac. So, to recap, I just need to know if I'm anywhere near the pieces of kit I need, including what kind of switch I need to trigger the timer. Thanks again!
 

Thread Starter

GuitarDemon

Joined Oct 16, 2019
4
22 ml in 2.7 seconds needs a 12V 7.5A motor? I can’t say I have any experience in dispensing liquids with a pump, but that sounds way over powered to me.

Bob
Hi Bob, there are 6 pumps dispensing simultaneously, each one uses 1.2 amps I'm told.
 

Tonyr1084

Joined Sep 24, 2015
4,539
I see there have been some posts while I was away looking at some pumps. Apparently you already have a pump in mind. Nevertheless, I'm going to post a video that features two pumps - a rotary pump and a vibratory pump. Both use AC. And I'm sure you can find them in 230 VAC models.

From what I've seen the vibratory pump is a bit noisy. But I also suspect it is more accurate. But then again, you say you already have a pump in mind. I'm wondering why you need 12 VDC. Nevertheless, you are the one setting the parameters of what you have, need and desire. So my video may be non-sequitur. Anyway, here:

 

MisterBill2

Joined Jan 23, 2018
6,076
It is not that difficult to deliver a time pulse set for a specific number of milliseconds, and that should be easily repeatable to the microsecond. It can be done with counters and a crystal time base, and amazingly enough it can even be done in hardware or software. The next question is how durable and reliable the system needs to be. If it is for parties at home then a bit less expensive, but if it is for making drinks in a busy bar in a night spot that is a bit different. The less expensive PLC devices from Automation Direct can be programmed in tenths of a second, and even better with more effort. And they will be reliable enough for almost any application. Even better, all of the pieces will make up a code-accepted package so there are no shock or fire issues. That may make spending a bit more easly worth the increase.
 
Top