Need help TIME Critical Project!!!

[jonwilhelmjr]

OK so engineering at its best with last minute work. I have my wedding reception September 29th 2018 and I am building a drink robot (machine) to dispense the cocktails 16 oz a cup in under 1 minute. So far i have the housing and other mechanical's built. Now its time to spin up a board fast and in a hurry. On my breadboard, I have working a Teensy 3.5 (5 Volt tolerant), tip31ag (5 volts on) transistor, 12 volt peristaltic pumps, and hall effect encoder if i choose to use it. This is a slow application my encoder produces 3 pulses per revolution at 20 Hz. I am updating/controlling 10 motors. Now on to my question.

A good engineering friend of mine , i.e. the programmer for this project, is very adamant that i take every precaution to separate the 12 volts from 5 volts and place ferrite beads, capacitors, and etc in circuit with the motors. I am not here to deny his concerns, i think he is right. What i want to know is because of my slow speed can i just put a 0.1uF cap on the motor leads and call it good? I don't have the time to over engineer but i also don't want to worry about this thing while I am on the dance floor of my wedding party. I hope to do this right (well enough) the first time. For my power rails, I had planned on 12 volt lead acid batteries for power. This will come in on a terminal block where i will then split off to the tip31's/motors/diodes and 5 volt linear regulator (possibly 7805, 10uF to gnd on input 12v and 1uF to gnd on output 5v). How should i separate the grounds? Looking for as simple as possible.

Please any help you can provide as i don't have time to order more than 1 board version. I'll post schematic pictures as i go.

Thank you all,
Jon

[julianhigginson]

Why make a custom board? it's just 1 (or maybe a couple) unit(s) you need?

It sounds like the kid of thing you can hack together with off the shelf bits and maybe some veroboard for bringing some pieces together.

Best thing with this approach is if you build it and the device isn't reliable, you have all the room you need to swap/change/add/remove anything you need to.



But... if you really want a professional review of a PCB design, best to show the schematic at least, and the existing layout, if it's started yet. Plus documentation of the housing and where everything will go, including pumps, valves, power supplies, etc.

[jonwilhelmjr]

I will share all the documentation I have as it becomes available. I do have proto board i can use but for as long as i have some time I want to order 1 controller board. If i implement the hall effect, i will have to order 7 more pcbs to attach to the remaining pumps.

[sokoloff]

For a one-time thing like this, I agree with using COTS boards and cobbling together.

I’d probably order both H-bridge motor drivers as well as simple relays for the drives.
I bet you can get close enough with simple timing and not need closed-loop feedback on the system.

I’d be more worried about health/cleanliness concerns, having an E-stop to shut off for “went crazy” concerns, and most importantly, how to prevent over-serving attendees who think it’s cool and go nuts in a way that a human server would cut off than I would about whether the Manhattan had an extra 0.4 mL vs the recipe.

[jonwilhelmjr]

Very good points made, here are some pictures I have so far. I have a video too once I can upload it

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[jonwilhelmjr]

All fittings are stainless steel 304. I will be running 95% isopropyl alcohol to clean before use. Silicone tubing as well.

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[Mr. Scram]

The choice to use this wood seems a bit strange, but I do like the shape!

[jonwilhelmjr]

The choice to use this wood seems a bit strange, but I do like the shape!

It was free good quality wood from work

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[jonwilhelmjr]

The choice to use this wood seems a bit strange, but I do like the shape!

It was free good quality wood from work

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Plus rustic wedding theme, I guess

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[jonwilhelmjr]

8 pump flow test

https://youtu.be/z6vHwmKTvEk

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[sokoloff]

If you do go with a timed dispense, maybe see if you can tilt the bottles in the device to minimize the head change between full and empty. Much less of an issue with a positive displacement pump, but may have an effect even there.

Good call on stainless. Was going to be my first question when I saw the pic, but you obvs have that covered.

[tpowell1830]

Similar to Great Scott's design?

[jonwilhelmjr]

Similar to Great Scott's design?

Thats exactly what i am trying to do but just means there is plenty of room for improvement.

[jonwilhelmjr]

Here is the progress I have so far. Please give me the honest truth I have thick skin. I do have a L293 version in the works. Lastly I plan on mounting the transistors to aluminum

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