# Ways of dispensing fluid for drink-making machine **URL:** \ **Category:** Factual Questions\ **Created:** [July 27, 2012, 2:44am UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525 "2012-07-27T02:44:10Z")\ **Posts on this page:** 12\ **Page:** 1
**Author:** ![BrandonR](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@BrandonR](https://boards.straightdope.com/u/BrandonR)\ **Post date:** [July 27, 2012, 2:44am UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/1 "2012-07-27T02:44:10Z")
[This](http://www.margaritavillecargo.com/video.aspx?vid=176) has inspired me to make my own cocktail-making machine as my next Arduino project. I’ve seen several other DIY drink-mixing machines but the decent ones look super expensive to make. I think the most difficult part is going to be figuring out how to dispense/measure the liquids. I don’t have any experience with fluid control but I have a few ideas… Pumps - get some cheap aquarium pumps with tubes that run in various alcohol bottles. But I’m guessing pumps don’t produce a constant volumetric flow rate so measuring the amount of alcohol dispensed might be tricky… Plus they’re noisy. Solenoids - invert the liquor bottles with a tube running out of each one attached to a solenoid. Again, the flow rate is going to depend on how much liquid remains in each bottle so that’ll lead to inconsistent drinks. Plus I’m not sure there’s a good way to get a good seal while the bottles are inverted with nothing but a hose coming out of their neck. Any ideas for a good, cost-effective way to do this? ---
**Author:** ![beowulff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/beowulff/32/542_2.png) [@beowulff](https://boards.straightdope.com/u/beowulff)\ **Post date:** [July 27, 2012, 3:07am UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/2 "2012-07-27T03:07:54Z")
Generally, this is done with a peristaltic (dosing or metering) pump. [Here’s](http://www.ebay.com/itm/Dosing-pump-Peristaltic-dosing-pump-for-aquarium-DIY-/160850944525?pt=LH_DefaultDomain_0&hash=item257376a20d) an example. You could also use stepper motors to drive a syringe, or use sensor to determine when a particular level was reached in a measuring container, then dump it. ---
**Author:** ![gotpasswords](https://avatars.discourse-cdn.com/v4/letter/g/c57346/32.png) [@gotpasswords](https://boards.straightdope.com/u/gotpasswords)\ **Post date:** [July 27, 2012, 3:10am UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/3 "2012-07-27T03:10:36Z")
How about an IV pump or an enteral feeding pump? Good accuracy, and eBay is full of them, starting at $20 or so. ---
**Author:** ![drachillix](https://avatars.discourse-cdn.com/v4/letter/d/48db29/32.png) [@drachillix](https://boards.straightdope.com/u/drachillix)\ **Post date:** [July 27, 2012, 6:11am UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/4 "2012-07-27T06:11:24Z")
or you can just order one of these [http://digitalbeverages.com/virtualbartender.htm](http://digitalbeverages.com/virtualbartender.htm) ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [July 27, 2012, 6:27am UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/5 "2012-07-27T06:27:33Z")
You could have a chamber that fills when a solenoid opens at the top (then closes when the chamber is filled), after which, another solenoid opens the bottom to drain the measured shot. Or just use a single powerful solenoid to operate a conventional bar optic measure. ---
**Author:** ![BrandonR](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@BrandonR](https://boards.straightdope.com/u/BrandonR)\ **Post date:** [July 27, 2012, 11:21am UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/6 "2012-07-27T11:21:39Z")
> [@drachillix](#): > > or you can just order one of these > > [http://digitalbeverages.com/virtualbartender.htm](http://digitalbeverages.com/virtualbartender.htm) Awesome as it is, I’m not sure I’d like to spend $3500+ on this project… I’d rather spend that money on the booze. 😉 I’m interested in the peristaltic pump idea – my ignorance about pumps prevented me from knowing there were ones capable of delivering essentially constant flow (guess I was only thinking about centrifugal-style pumps). Now of course I could have a pump for each liquid but I’m thinking I could also have one pump and a bank of solenoids that only opens the flow to one liquid at a time. Thoughts on the either approach? ---
**Author:** ![AaronX](https://avatars.discourse-cdn.com/v4/letter/a/7bcc69/32.png) [@AaronX](https://boards.straightdope.com/u/AaronX)\ **Post date:** [July 27, 2012, 11:49am UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/7 "2012-07-27T11:49:22Z")
Would it be easier to get auto-dispensing spouts for each bottle and just tip them over with motors? I mean those spouts that dispense e.g. 15 ml every time you tip the bottle over. ---
**Author:** ![HoneyBadgerDC](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/honeybadgerdc/32/1033_2.png) [@HoneyBadgerDC](https://boards.straightdope.com/u/HoneyBadgerDC)\ **Post date:** [July 27, 2012, 1:38pm UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/8 "2012-07-27T13:38:57Z")
You could have your bar bottles sitting on a scale and press a button to remove 1 oz or 2 oz whatever. About 5# of nitrogen pressurizing the bottles would give a nice gentle flow rate. It would require a hose and spicket for each whiskey. ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [July 27, 2012, 2:20pm UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/9 "2012-07-27T14:20:39Z")
> [@AaronX](#): > > Would it be easier to get auto-dispensing spouts for each bottle and just tip them over with motors? I mean those spouts that dispense e.g. 15 ml every time you tip the bottle over. In many ways that would be the easiest to do. Gravity fed systems have the problem of leaking valves. Pumps are complicated, and leave a lot of residue in the pumps and tubing after use. Pressure methods are complicated, potentially dangerous, and have the problem of leaks in valves and connections. There should be a way to put the bottles on a rotating rack that turns to select the one to pour, and then a single linear actuator tips the bottle to pour, then returns it to the upright position. The drawback might be that bottles that are nearly empty won’t dispense right. ---
**Author:** ![buckgully](https://avatars.discourse-cdn.com/v4/letter/b/eb9ed0/32.png) [@buckgully](https://boards.straightdope.com/u/buckgully)\ **Post date:** [July 27, 2012, 7:19pm UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/10 "2012-07-27T19:19:57Z")
There’s a lot of different approaches used at Barbot: > **[Drinking In The Future at Barbot SF 2012](https://makezine.com/article/home/food-beverage/drinking-in-at-barbot-sf-2012/)** > > Most of the Barbots and their teams are returnees from previous years, but as with the DARPA Grand Challenges, the...ah... bar raises very quickly from one event to the next as the innovations pour forth. This year's bots were all beautiful, with... If you dig around, most of those bots have build blogs out there on the net. For example, this one from my friends at Evil Mad Scientist Labs uses breast pumps: [http://www.evilmadscientist.com/2010/drink-making-unit/](http://www.evilmadscientist.com/2010/drink-making-unit/) ---
**Author:** ![bizzwire](https://avatars.discourse-cdn.com/v4/letter/b/958977/32.png) [@bizzwire](https://boards.straightdope.com/u/bizzwire)\ **Post date:** [July 28, 2012, 11:14am UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/11 "2012-07-28T11:14:49Z")
> [@BrandonR](#): > > Now of course I could have a pump for each liquid but I’m thinking I could also have one pump and a bank of solenoids that only opens the flow to one liquid at a time. Thoughts on the either approach? You’ve just described the ‘solvent selection valve’ that can be found on many high performance liquid chromatographs. You can buy them from [Rheodyne](http://www.idex-hs.com/about/data_sheets/idexhs_rheodyne_solvent_transfer.pdf) or [Waters](http://www.waters.com/waters/library.htm?cid=511436&lid=1530893), among others. They can be controlled by contact closure or RS-232. ---
**Author:** ![BrandonR](https://avatars.discourse-cdn.com/v4/letter/b/779978/32.png) [@BrandonR](https://boards.straightdope.com/u/BrandonR)\ **Post date:** [July 28, 2012, 2:58pm UTC](https://boards.straightdope.com/t/ways-of-dispensing-fluid-for-drink-making-machine/629525/12 "2012-07-28T14:58:06Z")
> [@badger5149](#): > > You could have your bar bottles sitting on a scale and press a button to remove 1 oz or 2 oz whatever. About 5# of nitrogen pressurizing the bottles would give a nice gentle flow rate. It would require a hose and spicket for each whiskey. Can you expand on pressurizing bottles? Obviously if I went this route I’d pour the liquors in bottles that can be safely pressurized but I’m not sure I understand the logistics of adding air pressure in bottles. Would I just have a hose in the liquid for extracting the fluid and another hose in the empty space in the top of the bottle to give it air pressure?