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Forum Index : Microcontroller and PC projects : WebMite in Silicon Chip Magazine
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Mixtel90 Guru  Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
Ah - didn't know you'd need that size. I was looking at the plastic 1/2" ones, which I thought might be ok for garden sprinklers. Mind you - I haven't even got a garden to speak of. :) Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| pd-- Senior Member  Joined: 11/12/2020 Location: AustraliaPosts: 122 |
This is for our food garden , so a mix of drippers for the fruit trees misters for seed raising boxes and raised beds with inbuilt 200l tanks  Theirs a flote switch to shut off filling when the tank in the bed is full There is not enough flow capacity to just turn everything on at once so you need to stagger each section. and different things need watering at different times. Edited 2023-09-09 21:24 by pd-- |
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Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3194 |
It occurred to me that if you are using DC to drive the solenoid valves you will need a different solid state relay as the ones specified in the parts list are for AC only. A substitute should be OK as these relays have a common foot[print. Geoff Geoff Graham - http://geoffg.net |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
That was why I suggested my two-transistor circuit, Geoff. It's probably a lot cheaper than a DC SSR and could be driven directly from the Pico. You don't need the opto-isolation for DC. The output stage could be a mosfet if the solenoid needs too big an inrush for a transistor. The available current from the capacitor could be appreciable then. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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| DaveJacko Regular Member  Joined: 25/07/2019 Location: United KingdomPosts: 76 |
do consider the ULN type ICs, been using them since the 80's to power flashing lights on arcade games. 7-way Darlington with on-die freewheel diodes in good ole 14DIP chips. 3v3 models available, sorry forget the part No. maybe ULN2003 |
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| Mixtel90 Guru Joined: 05/10/2019 Location: United KingdomPosts: 6798 |
The ULN chips are excellent but you need to be careful what you are driving with them. I'm not sure they'd have the capability of driving these 24VDC solenoids but fine for small relays. They certainly couldn't handle a 24VAC solenoid on 24VDC. Mick Zilog Inside! nascom.info for Nascom & Gemini Preliminary MMBasic docs & my PCB designs |
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Hans Senior Member Joined: 18/10/2022 Location: CanadaPosts: 116 |
Uln2003a data sheet says 50v but only .5 amps. Hans …  https://www.ti.com/product/ULN2003A?utm_source=google&utm_medium=cpc&utm_campaign=app-psil-null-44700045336317383_prodfolderdynamic-cpc-pf-google-wwe_int&utm_content=prodfolddynamic&ds_k=DYNAMIC+SEARCH+ADS&DCM=yes&gclid=CjwKCAjwr_CnBhA0EiwAci5siut2sfyGwi8r_tgxzalvjA8HVnilVBDNnnL2pAi7K3VwqZ5rv8QechoCh5EQAvD_BwE&gclsrc=aw.ds#product-details Edited 2023-09-10 08:47 by Hans |
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| Andrew_G Guru Joined: 18/10/2016 Location: AustraliaPosts: 847 |
Hi Geoff, I've nearly finished bench testing your Watering System (it really is good): - 8 valves - Rain sensor - Flow sensor - yet to be tested - Sending shortened messages to HC-12 network (cobbled serial to pins 16 & 17) - Sending emails via SMTP2Go (I've got it working but I'm holding off on changing the code in case you do a new version shortly). - 1 'master' plus 8 'valve' 24V-5W ac globes representing 24V solenoids. With the aid of the globes I've noticed that when running a schedule and changing from one valve to the next the 'master' turns off and then back on with the new circuit. Is there sense, when going to a new valve, in leaving the master on (less wear and tear)? Cheers, Andrew PS: I was going to suggest also leaving the old valve on briefly while you opened the new one (to reduce 'water hammer') but that would have three valves on at once (if only briefly). |
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| Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3194 |
That should not be doing that. I'm finishing off V1.3 and will look at fixing it. Geoff Geoff Graham - http://geoffg.net |
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| Andrew_G Guru Joined: 18/10/2016 Location: AustraliaPosts: 847 |
Unless it is something I've broken while tinkering? I'm happy to test code etc. Andrew |
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| Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3194 |
Yes, I have just checked the code and the master valve is left on while the program is stepping through the sprinkler valves. It could be something strange at your end. Probably it would be best to wait for V1.3 (due tomorrow) and test that. Geoff Geoff Graham - http://geoffg.net |
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| Andrew_G Guru Joined: 18/10/2016 Location: AustraliaPosts: 847 |
Thanks Geoff. Andrew |
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phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
Andrew, what is the current rating of your 24V supply? The globes have quite a low cold resistance so when a new globe is switched on it may be causing the voltage to sag briefly, dimming the master globe. If you measure a globe's resistance with a DMM you can calculate the inrush current. Edited 2023-09-11 23:08 by phil99 |
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| Andrew_G Guru Joined: 18/10/2016 Location: AustraliaPosts: 847 |
My fault - sorry! I had a 33uF capacitor in series with the common to reduce the brightness. Taking that out removed the issue. The Master SSR now stays on as the system transitions through valves and goes out just after the last valve does (as Geoff intends). Phil: Good thinking, thanks. The supply is rated at 1000mA so I thought at x2 the fuse that would be enough? Cheers, Andrew |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
The rating of fuses (with the exception of expensive HRC types) is quite rubbery. As a rough rule of thumb the marked value is the current they will sustain continuously without blowing. A "standard" fuse is supposed to blow within 1 min. at double its rated current. When tested many take much longer and some shorter. A 2A fuse will probably blow with a short circuit, depending on the series impedance of the transformer, but 1A might be better. |
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| Andrew_G Guru Joined: 18/10/2016 Location: AustraliaPosts: 847 |
Hi Phil, Is the 24Vac 1A supply up to the task? (The 500mA fuse was specified by Geoff so who am I . . .) Cheers, Andrew |
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| phil99 Guru Joined: 11/02/2018 Location: AustraliaPosts: 2135 |
I imagine 500mA will be fine for 2 or 3 solenoids on at the same time. The valve manufacturer's data sheet should show how much current they draw to determine how many the transformer can supply together.. Otherwise measure the AC current of a solenoid. Another limit will be how many your water supply can handle at once. |
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| Andrew_G Guru Joined: 18/10/2016 Location: AustraliaPosts: 847 |
Geoff - please tell me if my questions are too detailed etc. I'm looking at the flow sensor code in 'Sub RunValve . .. ' I'm trying to output the amount of water supplied by each valve over its time in the sequence. It doesn't have to be in litres (but I could calibrate it) but I'd like to know if valve n is supplying the same as say valve x. This would be dependant on the sprinklers, tap settings etc. I'd adjust the taps and the durations accordingly to get the amount of water each 'crop' required. Am I right that just before the valve is stopped with: "Pin(Valve(RunV)) = 0" the variable 'AveF(RunV)' is the average flow for that valve over the duration of this time period ie "RunTime". Thus the number I want for each valve is 'AveF(RunV)' * 'RunTime'? Cheers, Andrew (I can't test it without getting our hotel room of 18 months very wet) |
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| Geoffg Guru Joined: 06/06/2011 Location: AustraliaPosts: 3194 |
The only fuse required is the 500mA Slow Blow for the 5V supply. The current drawn by the WebMite is less than 100mA but the big 220uF capacitor will draw a significant current while charging so this is why a 500mA Slow Blow fuse is specified. The power for the solenoid valves is protected by the two PPTC (Polymeric Positive Temperature Coefficient) fuses. Nothing more is required. BTW a typical 24V AC solenoid valve will draw a surge current of up to 350mA when energised then drop to a holding current of about 220mA. Only two valves (master + one sprinkler) will be on at any one time although the BASIC program will turn them on half a second apart to limit the surge and prevent a "hammer" effect. Andrew... no problems with the questions (although in a few days I will be on Norfolk Island for a week so I might be slow to respond). The program will ignore the flow for the first 5 seconds after a valve is turned on and then, after a further 30 seconds, record the flow and add it into the running average AveF(RunV). From then on it will just monitor the flow (sampled every 30 seconds) looking for a sudden change. If the change is a sudden increase that indicates a burst pipe and it will terminate the sprinkler immediately. If it is underflow it will continue with the watering cycle but record it as an error. At the end of a valve's watering time the variable ThisF holds the flow for the last full 30 seconds while AveF(RunV) will hold the long term average flow including the first 30 second sample for this run. Both of these record the flow as the number of pulses recorded over 30 seconds. You need to find the spec for your flow meter to convert that to litres per second then multiply by the overall run time (RunTime * 60) to get the total volume of water. If you wanted to record the flow you could make this change: Pin(Valve(RunV)) = 0 LogMessage "Valve #" + Str$(RunV+1) + "Flow rate: " + Str$(ThisF) If Len(FlowDetect) Then And the flow will be listed on the console. If you set the Const LogToFile to true (in the beginning of the program) it will also log the reading to the log file "log_current.txt" in the WebMite's internal file system. This would be handy as you could then retrieve the file using TFTP whenever you wanted and that would give you the various flow rates over time (plus a lot of other info). Geoff Geoff Graham - http://geoffg.net |
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| Andrew_G Guru Joined: 18/10/2016 Location: AustraliaPosts: 847 |
Thanks Geoff. Your patience is appreciated. I'm beginning to understand your program and will make the suggested changes. Enjoy your break. Cheers, Andrew |
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