Archive for the OpenSprinklette Category


Posted in OpenSprinklette on January 4, 2020 by asteriondaedalus

If you are using a module such as the one pictured below, to drive a single sprinkler solenoid, then you will note it will accept 7-30VDC in. So you will need a AC-DC conversion. A bridge and a 1000uF cap will do. If you are wanting something neater then aliexpress comes to the rescue with a kit option.

Final Opensprinklette designs (for now)

Posted in OpenSprinklette on January 3, 2020 by asteriondaedalus

Presenting the quad board. Added additional terminal blocks to help manage the wiring. Added prototyping area to allow for additional hardware hacking, including four terminals for additional I/O. Notice GND, +5V and +3.3V power rails.

Top side of Opensprinklette quad board
Bottom side of Opensprinklette quad board

Presenting the single board. Added additional terminal blocks to help manage the wiring. Brought as many pins out as I dared to a pair of headers (J1 an J2). J2 also has associated solder jumper (on bottom of board) to help with option of V1 or V2 of Wemos mini relay board. The solder jumper on the Opensprinklette V2.1 sets the mode of J2 pin 2.

If you are using a version V1 of the Wemos mini relay board you don’t have options, as D1 drives the relay and you don’t get then to use I2C. Jumper defaults J2 to Pin 1=D2, Pin 2= D3 and Pin 3= D4. You lose D0 in any event since its set aside for V2 of the Wemos D1 mini relay board.

If you are using a version V2 of the Wemos mini relay board you change the jumper on Opensprinklette single to set J2 to Pin 1=D2, Pin 2= D1 and Pin 3= D4 . Effectively you lose D3. You need also to change the relay driver pin on the Wemos D1 mini relay board to D0 (from D1), using the solder jumpers on the Wemos D1 mini relay board.

Top side of Opensprinklette single board
Bottom side of Opensprinklette single board

J1 pinouts


D0 and D3 are not that exciting to lose in either event. D5..D8 gives you access to SPI so you either have SPI if using V1 Wemos mini relay or SPI and I2C if using V2 Wemos mini relay. Not a bad trade off. Not to mention UART is also brought out.

RxTx pinouts

2Tx out
3Rx in

Et Voila!

Posted in OpenSprinklette on December 29, 2019 by asteriondaedalus

So, I rebuilt a brand new single relay opensprinklette board. I did notice, as I stripped the original, that the end of the electrolytic was a tad “swollen”, oh dear, oh well.

I had a new batch of 47V TVS, physically smaller than another batch I had previously bought. So, that means I don’t need hack at the boards to fit them. I thought the original problem was that I had was using a lower voltage TVS than I should have been. Only marginally I thought. It didn’t turn out that the slightly lower rated TVS was the problem, though hacking the board to fit the larger and thicker leaded TVS probably helped me fry that board. I likely jumpered lead to the wrong place or inverted something.

No matter. Turns out a clean build, with all the properly rated components, still sees the brownout after a few cycles.


So, I shorted the shutdown pin to the VIN as recommended.

I then set up a node-red test that turned the relay on/off with a 50% duty cycle with 5 seconds in each state. It has been running now for about an hour without failure. So the quirk is that the Pololu 5V down converter seems more sensitive than the 9V down converter.

I will still need to short the shutdown on the quad board to be sure. I am now ready for final versions of the two boards, with minor tweaks including additional terminal blocks to keep the wiring tidy.

I am in the process of playing with a Kotlin front end for Android to manage the home setup. That is really just a prototype as the home setup will start with a single quad unit. I will build HMI system up as I get a hang of Kotlin development.

Brown outs and all that jazz

Posted in OpenSprinklette on December 28, 2019 by asteriondaedalus

So, now having a DSO on the bench, I was looking forward to solving the problem of the brownouts on the openspriklette prototype boards.

I saw the brownouts on the single relay version. I had a sneaking suspicion I might not see the problem on a quad relay version. The reason is simple. The single relay version uses the 24VAC to 5VDC circuit but the Wemos D1 mini does not have power conditioning aboard as sophisticated as the Wemos D1 R2.

The Wemos D1 mini does have an ME6211 regulator to down convert 5VDC to 3.3VDC. The Wemos D1 mini does not have an 9VDC-24VDC input option, which drives the need for more sophistication in the power input stage. That means the Wemos D1 mini is reliant on the power conditioning provided by the off-board power supply.

So, I assembled a quad board. It has the D24V3F9 9VDC out by Pololu. Older tech, but that’s what you get from Australian stores. So, fun story, that quad board works fine. I even attached two solenoids and cycled them on/off simultaneously. No brownouts.

Fun fact though. I had not tied the shutdown to VIN on either design. The specs warn if you don’t you could get strange behaviour. So, I still need retest the single relay board with shutdown tied to VIN. The problem, I did rather hack at it with some component swaps. I did get the bridge pins around the wrong way. There was smoke. No matter, I had three boards made – OSHpark minimum quantity. So, I will build another board and re-verify the behaviour without the shutdown tied to VIN. I will then tie the shutdown to VIN to see if that helps.

Oh! The DSO. Didn’t need it for the quad relay board testing. Will need it once I build up a single relay board.

Seems good …

Posted in OpenSprinklette on July 27, 2019 by asteriondaedalus

I did a retake on the components required for the 24VAC to xVDC boards, used in opensprinklette, and realized that I had bought 100uF instead of 1000uF electrolytic. Little wonder it wasn’t helping in filtering the spikes caused in hot end because of solenoid activation/deactivation.

So, swapping out the 100uF with a 1000uF fixes the crashing wemos!

Almost. It runs for a while then … wemos fires up, I have a looping test in node read that turns the relay on/off every 5 seconds. The LWT will pop up after the widget goes quiet after a few cycles. I found it would reboot and start again, though would only cycle a few times before crashing. More often than not, I had to pull the powerpack from power board and restart.

Runs a treat otherwise, as long as you don’t turn the relay on. All 24VAC elements appear on the correct side (the other side) of the protection, so its a little perplexing.

3 options. 1) the cap voltage rating needs boosting, 2) the TVS is too tight versus the RMS of the 24VAC input, 3) the circuit I found is a dud.

I am actually waiting on delivery of electrolytics of a higher voltage rating. Jaycar only had 60V caps. The TVS rating was on a batch I got based on an example circuit for OpenSprinkler. It it works for that then surely it should here? In any event, I have a slightly higher rated TVS batch coming.

The design I borrowed appeared to opt for a 40V design target so the cap really should have room. It will likely be the TVS (I am hoping) and then we can move on.

Bigger IS better 😉

So far, not so good

Posted in OpenSprinklette on July 14, 2019 by asteriondaedalus

All testing good until I wire in a solenoid.

When you go to turn on solenoid, the wemos crashes.

I think I designed in a whoops, since the TVS protects from spikes on power from other solenoids, but not the one the wemos is controlling (I managed to have it on the wrong side of the TVS.

So far, so good.

Posted in OpenSprinklette on July 13, 2019 by asteriondaedalus

So. I will need to redesign, as I used too big a cap template. Otherwise, it seems to power the board fine. I will need bomb opensprinklette onto the wemos for some testing.

Out of shot is the 1 AMP 24VAC power pack.

Missing is still the single relay shield, to be plugged into the Wemos D1 mini.

The redesign will shrink the 24VAC – 5VDC section.