doser pump solutions - Page 1
Forum section: electronics / projects

author: m3vuv
author_rank: Super Contributor
timestamp: August 28, 2019, 08:01:29 am
content: hi all,ive got to design a chemical doser pump for a water authoratory,it needs to deliver 1.2 ltrs over 24 hrs be self contained a will be down in the sewars,i can use an arduino to trigger a mofet via a solenoid it needs a 1 second pulse every 10 seconds,the solenoid is 3watts at 12v,i calc i will need a 20ah battery to last 8 days,the arduino consumes about 83ma,is there a way to use a resistor to charge a cap and have it pulse a mosfet to fire the solenoid need to find a way of doing it using lower current,a 5ah battery would be better,any ideas?

author: KMoffett
author_rank: Regular Contributor
timestamp: August 28, 2019, 11:08:59 am
content: The solenoid is the current hog. 3W/12V=0.25A Average over 10 seconds is 25mA. You will still need the same total current to charge a capacitor to fire the solenoid. As far as the Arduino, you really don't need that much computer capability, unless there is other functions. A LM555C astable timer with a MOSFET on the output will draw less continuous current.

author: rhodges
author_rank: Frequent Contributor
timestamp: August 28, 2019, 11:33:33 am
content: Have you looked at peristaltic pumps? I have been working with them to pump oil. I have one with 2x4 mm tubing that pumps 31 grams per minute at 12 volts. One with 3x5 mm tubing pumps 76 grams per minute. These are the cheap ones on ebay (around $4 each.) I only measured current on one of them, it was around 260 mA at 12v. You can buy the silicone tubing separately so you can have a single tube from source to destination, or to replace the pump tube when it wears out.

author: m3vuv
author_rank: Super Contributor
timestamp: August 28, 2019, 12:01:41 pm
content: its not actualy a solenoid as such,its a custom shuttle valve assembly,using an electro magnet,to open it,the total on time for the electro magnet is 30 mins over 8 days to give the required dose,it worls out 1 second on time in every 10 if i remember,the reason for going that route is for the ip rights,cant realy patent it with a peristaltic pump,money isnt an object within reason,may go with a cmos 555 ic and cobble it together and measure that,mcdonnalds are currently trialing some,its to dose a chemical into sewers to break down fat,thats no probs for them as its mains powered thames water need one unatended down manholes,currently using a 20ltr bag in a box,the idea is to swap the bag in box every 8 days along swap the battery with a charged one,the market potential is huge!!

author: patrick1
author_rank: Contributor
timestamp: August 28, 2019, 02:33:25 pm
content: Hi, you inspired me too convert one of my circuts, into computer speak, - i created this circuit last year, and it has been very handy,many basic electronics things, can convert a short pulse into a long pulse, -but i needed somthing that does that backwards.im sure it would be easily adapted too a your needs, with the addition of the initial timer.Also i would recommend, adding a pair of decade counters too your 555 timer. - so your timer only needs too pulse every 6 seconds, instead of 10 mins.... much more stable that way, - i 4017's are time proven and stable, - i use them in my 1000v motor project ;=)Patrick,

author: m3vuv
author_rank: Super Contributor
timestamp: August 28, 2019, 03:58:07 pm
content: by the pic it seems as clear as mud,needs more info to my mind,ie complete chematic including the 555 ic connected,thanks tho.

author: KMoffett
author_rank: Regular Contributor
timestamp: August 28, 2019, 05:54:58 pm
content: If you want go with the 555, this will save you build time, but maybe not battery time.:https://www.jameco.com/z/MK111-Velleman-Adjustable-Interval-Timer-Kit_2265311.html?%20CID=GOOG&gclid=EAIaIQobChMIoIqd3pCm5AIV6__jBx2DtwBREAQYBCABEgLHmvD_BwEMaybe replacing the relay with a MOSFET would help.Ken

author: jmelson
author_rank: Super Contributor
timestamp: August 28, 2019, 07:10:59 pm
content: Quote from: m3vuv on August 28, 2019, 08:01:29 amA CMOS 555 should be able to do the one second on, 9 seconds off on practically zero current. Very simple circuit, look up 555 atsable online.Jon

author: patrick1
author_rank: Contributor
timestamp: August 29, 2019, 07:12:25 am
content: Hi good idea, i fixed my schematic.oh, and please disregard my comments about the 4017 decade counter, - - i missunderstood your requirment, i thought you needed 1 second every 10 mins, not every 10 seconds. - that way the 4017 can be used as a multiplier, giving you one output pulse - for every 100 pulses of the 555fixed diagram_\/

author: m3vuv
author_rank: Super Contributor
timestamp: August 29, 2019, 01:35:41 pm
content: hi my calculator for the 555 in astable mode says infinity on the resistor and cap values,i need on for one second and off for 9,has anyone know what the values should be?,cheers m3vuv.

author: patrick1
author_rank: Contributor
timestamp: August 29, 2019, 03:18:04 pm
content: for the 555, you will need too add a component, which is why it is not working in calculator.a diode is required too charge the capacitor via your pin 6 ? 2 link wire. stick the diode between pin 7 and pin 6, - with current being aloud too flow in that direction too.however if you use my circuit, - any 555 timer values will work, - even if your on time is 50/50 or 60/40, - my circuit will just output a brief pulse in response too any input, and reset itself for the next pulse. ... so basically you just need a 555 timer set too 10 seconds, - and the output will go into my pulse circuit, the output of which, is fed backwards through a zener too flatten it, - or forwards through a short string of diodes too flatten the signal .... and the results of that rigmoreall will go into your drive transistor.peace.