2 relays/110 v solenoids Polyurethane Machine

Hi All,

I think I am in over my head. I am looking to upgrade a couple of the basic controls on my foam processing machine (circa 1970's). There are currently 3 electric over air solenoids which control the dispense/flush cycles. As the machine is now the functions are as follows;

Dispense: ATC brand countdown timer which controls a 4 way, 110v air solenoid to a small (1" x 6") air cylinder. We set the timer in seconds (00.00) which actuates the cylinder (open) for the set time then closed. The cylinder mechanically opens two valves simultaneously which dispense two components (poly and iso) into a mechanical mixer. This mixer then needs to be flushed or cleaned out after each cycle.

Flush: This is a combination of two other solenoids, air and solvent. Currently when the dispense cycle is complete we have to go back to the machine and manually cycle between the solvent and air (push buttons) two or three times in order to clean out the mixer. If we forget or are too slow to to go through the flush cycle bad things happen.

At the minimum I would like to use the arduino for the flush cycle. This would need to be initiated by the end of the dispense cycle with a delay, possible alarm, followed by solvent, air, solvent, air, solvent, air. The program then would need to reset and be ready for the next cycle. To further complicate things we also have occasions where we dispense multiple times prior to flush ie. 5 separate 2 second dispense cycles then flush. If this is too complicated I don't oppose a separate manual flush button to initiate the cycle once we are done shooting the molds.

Here's my problem: I purchased a sainsmart uno starter kit and relay board. I understand some of the basic programs and can change the on/delay values. I need to know where I can find a basic program that i can alter to cycle the two relays along with the wiring schematic. I also need to know how do I get the program to start once the dispense cycle is complete or should i just go with the manual button after we are done?

Any input would be appreciated,


this forum is basically here so we can help you figure it out.

if you want to hire someone ( your project is easy enough to do in this forum ) becuae you are pressed for time or some such, there is a gigs and collaboration fourm. jut putting that out there.

I would suggest you make a time line and a schematic for your kettle, with each valve listed individually. use names that make total sense and then use them in the program. Flush_Solvent_1 and Poly1 and Iso1 and air1 and so forth.

work out a simple time line.

if you know you need 3 mix cycles before a flush, where to you set that ?

I think you could have a manual start for the flush. a light/strobe and horn saying you are ready. then you can tap the button and run the flush cycle. at least until you are 110% satisfied everything it working 110%.

but, it sounds like you have a simple process.

At this point, do the solenoids come back to one electric panel ? I would exect a simple box on the wall with power and all the relays in it that are wired to all the solenoids.

what you would want to do is to create an overlay of control so you can go from what you do now, to what you want to automate.

Thanks Dave,

So based on your comments, I think I'll go with the manual start to keep things as simple as possible. At least for now until I get a little more experience under my belt.

To answer your questions;

If I know that I need multiple mix cycles before the flush, I simply push the dispense button again after each cycle until I am ready to flush. I can only shoot consecutively the same cycle time.

The solenoids are not together. The way I have the machine set up is a main unit which contains the majority of the electronics and then there is a boom which extends out to the mix head. Two solenoids are on the machine and one is on the mix head. This shouldn't matter too much because the wiring all goes back to the machine.

For startup purposes my time line would be as follows;

Push flush button Alarm: 5 seconds Solenoid 1 (solvent): 1 second Solenoid 2 (air): 5 seconds Solenoid 1 (solvent): 1 second Solenoid 2 (air): 5 seconds Solenoid 1 (solvent): 1 second Solenoid 2 (air): 5 seconds Reset


I if you have a breaker panel, then the wires come out of that on circuit breakers. if the power goes to a solenoid, it has also have to go to a switch of some kind.

if you have a wall mounted panel and each separate circuit comes of out of that, then all your control wiring is in a cluster.

if each switch is near the valve, then your control wiring will need to be distributed.

if you want to automate the whole machine, then you would need to inferface with these bits.

ConceptOneMfg: For startup purposes my time line would be as follows;

Push flush button [test for other things either running or not running ] [pause 1/2 second] Alarm: 5 seconds [any button push would halt the process]

Solenoid 1 (solvent): 1 second [ pause 1/2 second ] Solenoid 2 (air): 5 seconds [ pause 1/2 second ] Solenoid 1 (solvent): 1 second [ pause 1/2 second ] Solenoid 2 (air): 5 seconds [ pause 1/2 second ] Solenoid 1 (solvent): 1 second [ pause 1/2 second ] Solenoid 2 (air): 5 seconds [ pause 1/2 second ]



for the startup, the solvent wash could just happen, or you could have a warning that it is ready and you have a 5 second delay to stop it, just in case.

since I am sure you do not want to dump solvent in at just any time, you would want to look at other bits of the system to make sure that everything is ready for a solvent wash.

We would just have to make sure that we don't mash the flush button while it is in dispense mode which shouldn't be an issue. I would separate the buttons so that one is activated right hand and the other is left.

The alarm is not necessary but would be nice to make sure everyone is clear. If it were setup to push it again and stop the cycle, that would be an added safety feature that I had not thought about, very cool..

There are currently two push buttons, one for solvent and one for air. I could tie into the "hot" side of each and go to the relay's. This should allow me to still manually actuate the solenoids, i think?? If not I could use a switch to set it on either manual or auto..

I am looking through some of my files to see if I have any pictures here at the house.

Thanks again,


as you probably know, lighting an LED shows the channel is working and the logic is too.

in your case, I would mock up a panel and put in some switches

I would also add a couple switches to simulate ‘other things’ going on. that way, you can have it time out after a batch or some such.

it is easy to do the toggle timing you want, so the program in it’s simplest form is easy.

how do you plan on interfaceing with the existing solenoids ?
I would think you could add a relay and wire parallel to them.

and that brings up the question of where you can install the relays.

As for relays, any time I get near industrial wiring, I want screw terminals.
here is a relay, ebay special. use arduino relay H/L level in the ebay search.

these have screw terminals for both the output as well as the input wiring.

the Nano is functionally the same as the UNO, it too is available with a screw shield.

the only caveat is find tiny standoffs and tiny screws for the darn things.

nano screw shield.jpg

Lets see if the file attaches, it is larger than the max size..

I assume that the screw shields plug into the top of the UNO that i have and is basically an adapter. I was kinda wondering how this was going to work with the jumpers included in the kit. I will order one as well as the screw terminal relays this evening.

I have the equipment to machine any type of standoffs and mounting plates necessary.

I was planning on mounting the whole rig somewhere on the outside of the main machine in it's own box so that I have access to the download port. The unit will be powered by it's own power supply which makes me wonder what happens if I plug the laptop in while it is powered by the supply?? Do I need to disconnect the power supply before plugging in the laptop?

For wiring the existing solenoids I was planning on just adding an additional wire from the hot side of the existing switches over to the common of the relays. Then out from the relay to the other side of the solenoids. There is a junction block already for the neutral..

Thanks again for all of your input, it has been very helpful. While I'm waiting for the rest of the parts to come in I will start to set it up temporarily on the dining room table. I'll post some pics this evening.


The NANO is a different board than the UNO. they act the exact same way and have (almost) the same functions.

the NANO has 2 extra analog input pins, but other than that, it is the same in function and design.

the board I linked was for a NANO, but they do make screw shields.for the UNO, I am not as fond as they sit on top, or you have to re-solder your pins.