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inie meanie
Yes you should rate your coils for your own current range.20 amps is more than enough for me.
Yes you should rate your coils for your own current range.20 amps is more than enough for me.
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bradburts
Please elaborate. Are you talking about the PFC chopping the AC? The EMMA seems to get by with a PFC and off the shelf filter. What filter would you use?
Otherwise the circuits I have seen have inputs protected with clamps, use opto isolators etc. I see no reasons why they could not meet CE so long as the build design is sensible.
Agree, being a lazy engineer is usually best.
I would try and tempt you from the off the shelf PID controller though. There are plenty of ready made microcontroller solutions you can buy for £20 or so. Most have worked examples showing you how to make an ADC readings and drive a DAC outputs (or analogue out using driving resistors from your output ports).
If your PID controller has built in analogue and digital buffers then I guess its the best thing to use. Your system is then pretty much COTS and you have a £200 EMMA! Which PID controller are you looking at BTW?
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pmcalli
To meet CE radiated and conducted emissions you need a filter designed for dirty circuits like thyristors. An off the shelf one is about £50. You also need to protect for failure mechanisms which could cause a fire so fuse is required for the thyristor or crydom unit. An MCB is required because the crydom unit and thyristors have a significant leakage current when off so regs demand a switch as its above 25VA
I have just been costing it up and it comes to more like £500. I am also having problems sourcing the PID controller to match the 10 V o/p cts that EMMA uses. they need a load > 2Mohms and the controller needs an external analogue set point. so I have been tempted to the dark side by my son and a colleague who have offered to lay out a pcb and do the micro controller programming . This should bring the cost to under £250
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bradburts
Would you mind posting a link to a suitable unit?
Thats a lot! I was expecting a lot less but I have not looked at the cost of the CTs.
I think that you are best going with a microcontroller. As pointed out the Arduino projects at openenergy monitor forums are well worth looking at.
There are examples showing how to log your systems performance to the cloud and then you can monitor your system from your smart phone or web browser. You would struggle to do that with a PID controller + the extra cost of the PID controller.
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pmcalli
Would recommend a two stage filter Buy Power Line Filter 2 stage chassis mount filter,16A Schaffner FN 2060-16/06 online from RS for next day delivery. this one is under £30 you can get a single stage for half that but not sure it would pass CE. DIN rail mounted ones are available as well but horribly expensive £100 touch
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bradburts
Thanks.
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suntrap
In that case, how about going all the way and using a triac (opto-isolated ones available for about £5) rather than the Crydom controller? Get a sniff of AC voltage and generate the trigger pulses yourself.
S
suntrap
Or if you really wanted to economise you could buy a couple of washing machine filters (they seem to be single-stage) and put them in series. They can handle the current. I did wonder if the suppression would be less effective due to the size of a washing machine motor, but the component values seem to be comparable.
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bradburts
Yes, I would go all the way on the TRIAC.
Generating the pulse yourself would be easier than interfacing to the Crydom.
To generate the pulse you just need to detect zero cross - a diode on a digital input would do (some braver sole may forget the diode and just use the digital input's ESD protection). Arm a counter counting down from the DIO trigger and you're done. OK some calibration needed. All microcontrollers will have a counter and/or PWM on board.
With the Crydom you have to generate and buffer an analogue signal using a DAC or resistor chain. Needing an onboard DAC is going to heavily cut down on your microcontroller choice. There are plenty available but perhaps not on a ready built evaluation boards.
I am digital & find analogue tricky, perhaps you're the other way. The timer / PWM arm software is just a few lines and there will be plenty of examples available.
If you use DIO then you just need an analogue circuit to protect the CT inputs. If you buy an microcontroller evaluation board then there should be space enough in the prototyping area to fit that circuit.
Without knowing your CTs cost I would say that your down to £100 or so with your line filter.
Evaluation controller £30 + £5 TRIAC + Case&Heatsink + £5 CT clipper + CTs + On/Off switch & fuse + £30 line filter.
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pmcalli
Yes I find the analogue easy as I have experience in phase lock loops and analogue control loops. The crydom is attractive only as no interfacing at mains voltage is required and I don't have to design a snubber which is notoriously difficult to test without creating a bucket full of dead bits. I may also consider the option of an entirely analogue loop with a micro-controller to supervise,feed a display of power, logging and some load switching. I need to get on and build a prototype ( pressure from a queue of friends who followed my advice with the PV system and want the immersion controller ) and so will probably postpone the triac for a phase 2 cost reduction. Many thanks for the inputs very useful
Sacreblue! I can sell you one for under half that or as a kit for even less, but fine if you prefer the challenge of designing your own. Mine do work, as stated by early adopters such as:-
From a retired CEO of a housing authority:-
After some fine tuning the I2 worked well. I can tell from my web based power monitoring system that the unit cuts in and out at the right times. On a sunny day it provides all the hot water we need.
From a qualified electrician:-
The unit is working really well and keeping the thermal store topped up with heat on the days where I might not have usually produced quite enough from the solar thermal system.
I was monitoring the system the other afternoon and taking measurements with my clamp on wattmeter. This can differentiate between import and export power and shows a negative reading on export. Watching the meter keeping the power exported to around the 50-100W mark while the PV system was generating 1-1.2 kW, I observed the current to the immersion was gradually reduced down to 0.3 amps and then go off as the sun dropped in the sky.
I will probably be looking to buy another unit from you to install in my Mother's house as she has just had a PV system installed.
(To be fair not everyone is yet getting that low an export but it's an adjustment issue I think).
From an airline pilot:-
I have now the means to measure import/export accurately! Your device works perfectly and does exactly what you say! Very happy.
T
trebormint
we have developed a system which connects to a standard 3KW immersion heater which will reduce the power consumption to a more acceptable 1.2KW. It monitors the array output & household consumption & will switch the heater on when the PV is generating enough & switch the heater off when either the PV isn't producing enough or if the household consumption increases above the demand for the PV.
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bradburts
Sounds interesting.
Please share for others to build with/on. How did you go about it, which design did you use?
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pauldreed
Who is we?
What is your professional status, are you a registered company?
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pauldreed
Wot, 5 day's later and no response??
hmm.... is it me and my mate Fred who knows a lot about lectric stuff?
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trebormint
I'm sorry to have kept you waiting; I don't visit the forum every day.
The device I mentioned is a being tested at an installation in Southampton. When we're completely satisfied with it's performance I'll post a thread giving more details.
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suntrap
Another commercial product then? Why are people being so clandestine about them? Are they worried that they are infringing patents so are only giving details to people who approach them privately? Doesn't cost anything to make a website giving full details of what you are trying to flog.
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pauldreed
I agree Suntrap!
I suspect that they do not believe that their designs would survive scrutiny, and hide behind this 'patent' rubbish. If I am wrong - please post your patent registration details here and surprise me!
I have no commercial interest, but if you want to see how my system performs click here to see real live stats.
...and to see how I got there, see my blog powerhub.info
It would be good for the commercial developers to do similar...
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inie meanie
As a follow up to the filters quote. I have purchased a Schaffner 2060-16/06 for £2.88 off ebay. All fited within half an hour, just at the output of the Triac. I have since found out that that all electronic apparatus sold or taken into service within the EU must comply with the essential requirements of the EMC directive 2004/108/EC. Failure to do so is a criminal offence in the uk.
Sounds a bit heavy handed but you can buy these very effective two stage filters on ebay very cheaply in an auction or as a buy it now , see links
eBay - The UK's Online Marketplace
eBay - The UK's Online Marketplace
http://www.ebay.co.uk/itm/250892028047?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2648 other auction sites are available :- )
or just search for 'Schaffner FN2020A-20-06 ' these are for £12 inc delivery so too cheep not too!
Thanks to the members for bringing this to my attention.
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pauldreed
That's probably why they are on DealExtreme!!
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inie meanie
Well it must depend on their design.If they don't use a triac then they dont need any thing I suppose. Just a regulated output via a FET etc they won't have that problem.
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chriswarhurst
Hello all,
New to this and picked up a google search thread - my company has developed a 240v low power immersion heater for domestic installation that incorporates 2 elements a 250w and 500w into one immersion heater. The idea is that it compliments your solar PV array and heats your water tank up slowly throughout the day. Starting at 250w, switching to 500w, then switching both on which gives you 750w then back to 500w then 250w later in the day. It works really well - we received the prototype last week and it works really well on its own connected to a simple timer. If you have developed a switching system tied to the inverter then I would be really interested in talking to you about it. contactable on [email protected]
New to this and picked up a google search thread - my company has developed a 240v low power immersion heater for domestic installation that incorporates 2 elements a 250w and 500w into one immersion heater. The idea is that it compliments your solar PV array and heats your water tank up slowly throughout the day. Starting at 250w, switching to 500w, then switching both on which gives you 750w then back to 500w then 250w later in the day. It works really well - we received the prototype last week and it works really well on its own connected to a simple timer. If you have developed a switching system tied to the inverter then I would be really interested in talking to you about it. contactable on [email protected]
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pauldreed
Hi Chris, what length is the element(s)? and does it have a inbuilt thermostat?
... oh, and how much money!!
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chriswarhurst
The immerser is made from Incoloy - 11” long with a standard 21/4 inch BSP thread. 240v TWIN element version 1 x 500w and 1 x 250w including two 7” stat pockets and two TSDR stats. If its a one off purchase its £110 + VAT if you are looking at bulk we can come down in price. Got to say the figures it producing so far are fantastic - effectively it is raising the water temperature high enough so that the boiler is currently switched off - and for free as the power it is drawing is within the output of the 3.8 Kw Solar Array. Watching the performance closely as we head into the winter months. Hope this helps
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suntrap
No, they are standard switch-mode designs (power supplies, not power controllers) which all need mains filtering. Their PCBs have positions for filtering components but these are all missing!
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suntrap
Unfortunately, connecting it to a timer is a very inefficient way of maximising your use of solar power whilst minimising (or for most, preferably eliminating) your draw from the grid - the difference between output when the sun is shining and on a dull day is easily a factor of ten and a timer cannot predict this.
Read this thread and you will see that there are several such systems, one (sadly, only one) of which has had all its details published and made available on a royalty-free basis.
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pauldreed
Chris, this sounds very much like an element designed for boats - not domestic hot water systems, and for the majority of this thread's readers would be unsuitable for the following reasons;
1) As suntrap has commented, using a timer is inefficient as on dull days, the power would be drawn from the grid, therefore a more complex switching solution should be sought.
2) Hot water rises to the top of the tank, therefore if top mounted (as is the norm) then this element would only heat the top 11", leaving the majority of the tank cold (would work OK if it could be bottom fitted).
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chriswarhurst
Its an adaption of a standard immersion heater that uses two low power 240v immersers - we can do an 11 inch or 27 inch for larger tanks. The timer I agree is a crude mechanism balanced against a 3800 w Solar PV system. The array puts out 400w on the most cloudy rainy day so 250w from 0900 till 1500 hrs is background power consumption. The 500w element kicks in at 1130 till 1330 so still well within average power tolerances. You are right in that the switching mechanism is suboptimal but I disagree with the word inefficient it depends on the cost basis. A simple electronic timer costs £38. A bespoke emma unit is over £1000 so the cost benefit analysis over time against a viable use of the energy in heating hot water actually makes it very efficient.
As far as the tank is concerned - this is designed to sit in the top third horizontally so it only heats up the top 100 Ltrs or so. That means it is not wasted in trying to heat the whole tank up - something that it just does not have the power to do. 100 Ltrs of water is enough for average normal domestic use. Modern mains pressure systems have the immerser mounted horizontally in the top third of the tank. This system is not designed to sit vertically at the top of the tank as is common with older HW cylinders. Its not perfect but it is working and producing free hot water. Hope this is of use
As far as the tank is concerned - this is designed to sit in the top third horizontally so it only heats up the top 100 Ltrs or so. That means it is not wasted in trying to heat the whole tank up - something that it just does not have the power to do. 100 Ltrs of water is enough for average normal domestic use. Modern mains pressure systems have the immerser mounted horizontally in the top third of the tank. This system is not designed to sit vertically at the top of the tank as is common with older HW cylinders. Its not perfect but it is working and producing free hot water. Hope this is of use
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pauldreed
Yes but how much power is being used in your home... fridge, freezer, etc, offset home consumption against your 400W, and there won't be a lot left for the immersion heater.
IMO inefficient is an accurate description! if you put the washer on, boil the kettle, dishwasher etc. where does the power come from to power the immersion heater? The grid of course, which is kWh chargeable.
You havn't grasped the concept of this thread!
We are trying to develop cost effective control systems, albeit in different ways, which cost far less than £1,000 and nearer the £38 mark.
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chriswarhurst
Let me know when you have developed one - i will be very interested
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suntrap
He already has - and all the information about it has been published. Look through this thread if you want to know.
I've been working my way through this thread for days. Really interesting and a credit to the contributors. Its taken days because I'm a chartered (mech) eng so can only deal with things that can be measured in buckets. No, I've 16th Ed and did hobby electronics years ago so I think I have the skills, if not the electronics knowledge, to have a go at building a simple,safe, economical controller for an existing 3kw Immersion heater.
Was surprised at how little the potential savings were, though. Checking the gas meter these past few weeks without heating on, converting to kWh, and plugging in the cost per unit I reckon about 50p per day on HW. In summer its likely HW will max out on the temp stat part way through the day and in winter it'll struggle to put much surplus into the HW tank. So maybe 1/3 of the annual cost will be saved - say £60 - which is worth having but limits options - yeah I know its a crude calculation but probably not wildly out.
Can I just ask a few questions ,which I hope are not too stupid, asked on the basis of 'will it work' not "is it the perfect solution"?
I want to use the Arduino (no experience, I'll have to learn) as it seems to be a well supported, flexible platform for development and communicating. Am I right that 2 suitably sized LEM CT's will hook up fine to the inputs? Think I read here somewhere that something else was needed but cant see where and cant think why.
The Crydom and filter (at the right price) + fuse & MCB looks the proprietry, proven way to control the 3kW load. Since it doesn't like PWM I thought a suitable compromise might be to use an R-2R ladder and an Op-Amp to double the voltage.
Digital to Analog converters (DAC), using R/2R netwroks
Suitably programmed the Arduino would step the output voltage applied to the Crydom which would raise or lower the immersion heater power. Not perfect DAC but a good 80:20 pereto solution I thought.
If this is totally out of court can someone please suggest and illustrate / point me to a suitable way of achieving this? I would need to be taken through Triacs, etc as they came after my hobby days.
Was surprised at how little the potential savings were, though. Checking the gas meter these past few weeks without heating on, converting to kWh, and plugging in the cost per unit I reckon about 50p per day on HW. In summer its likely HW will max out on the temp stat part way through the day and in winter it'll struggle to put much surplus into the HW tank. So maybe 1/3 of the annual cost will be saved - say £60 - which is worth having but limits options - yeah I know its a crude calculation but probably not wildly out.
Can I just ask a few questions ,which I hope are not too stupid, asked on the basis of 'will it work' not "is it the perfect solution"?
I want to use the Arduino (no experience, I'll have to learn) as it seems to be a well supported, flexible platform for development and communicating. Am I right that 2 suitably sized LEM CT's will hook up fine to the inputs? Think I read here somewhere that something else was needed but cant see where and cant think why.
The Crydom and filter (at the right price) + fuse & MCB looks the proprietry, proven way to control the 3kW load. Since it doesn't like PWM I thought a suitable compromise might be to use an R-2R ladder and an Op-Amp to double the voltage.
Digital to Analog converters (DAC), using R/2R netwroks
Suitably programmed the Arduino would step the output voltage applied to the Crydom which would raise or lower the immersion heater power. Not perfect DAC but a good 80:20 pereto solution I thought.
If this is totally out of court can someone please suggest and illustrate / point me to a suitable way of achieving this? I would need to be taken through Triacs, etc as they came after my hobby days.
methley
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I'm building one right now with an Arduino Uno board which is perfect for this job. For the output, the R-2R ladder uses too many outputs. As the Arduino supports PWM outputs all you need to do is filter the output of a PWM pin and add a voltage doubler to drive the input of a Crydom. The Crydom takes away any difficulty in driving a Triac. It's all there in one package, and is fed simply with a 0-10v input.
For the inputs from the LEM's you'll need to half the voltage, using a simpler resistor potential divider. Note the minimim load on the output of the LEM is 2MOhm.
For the inputs from the LEM's you'll need to half the voltage, using a simpler resistor potential divider. Note the minimim load on the output of the LEM is 2MOhm.
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pauldreed
My Arduino based device is here if you are interested.
The first version was built with a Arduino Uno, but my current one uses a £4 Arduino chip (Atmega 328PU) along with a few support components, and runs the same software.
The credit however must go to these guys.
The first version was built with a Arduino Uno, but my current one uses a £4 Arduino chip (Atmega 328PU) along with a few support components, and runs the same software.
The credit however must go to these guys.
Methley, have you successfully got the Crydom working via PWM and filter? Crydom advised me "The analogue DC input is sensed by a micro-controller, a PWM input would either not be recognized or falsely interpreted. The PWM signal would have to be converted to DC signal." which led me to doubt that a filter would give a clean enough input, and as a result might damage or overheat it.
Paul, I've been impressed with the development you've put into this, as witnessed by this thread and others. I'll read up the links and try to get some understanding of what you and these guys have been doing. Might be a bit advanced for me I fear :-(
Paul, I've been impressed with the development you've put into this, as witnessed by this thread and others. I'll read up the links and try to get some understanding of what you and these guys have been doing. Might be a bit advanced for me I fear :-(
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pauldreed
I too spoke with Crydom some months back, the problem with PWM is inherently the speed of the sampling rate is too fast for the Crydom Thyristor circuit to recover, and therefore would not work.
I think Methley has taken the PWM output through a capacitor/resistor circuit to smooth and average the peak value, similar to this.
The input would be clean enough, but there is a lot of debate around the switching harmonics/distortions caused by the thyristor.
As for being 'Advanced', this was my first project for over 30 years when valves were the norm, so if I can, so can you, just take your time and if you get stuck there is plenty of help in the forums :->
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suntrap
That sounds very plausible and does make it less attractive if you are offsetting the cheapest fuel - mains gas. Same problem there has always been with solar water heating: loads in the summer and not enough in the winter. And you could also argue that offsetting gas consumption with electricity is not very environmentally friendly. I did ponder the idea of overriding the freezer thermostat to reduce its consumption from the grid at night, but of course that's a fairly small fixed load and has the additional complication of not liking to be short cycled.
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suntrap
There is a 5V version available.
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pmcalli
I have now built and tested two immersion controllers so thought I would share the results.
the first solution used a PID controller crydom and true rms ct's which as people here have pointed out is a very expensive solution.
results
The true rms CT's are loaded by the PID controller this does not affect the operation but is undesirable.
the response time of the true rms cts is 300ms so the PID integration time had to be long
very small grid feed in with large load changes otherwise results good.
the second solution uses some inexpensive ops amps the crydom controller and a couple of owl ct's.
results
the cost is very low the owl ct's are obtainable for about £6 each op amps and other components are less than a £1. crydom is about £70 filter £25 power supply £10
response time is set at 100ms and no grid feed in or consumption is measurable.
As there has been many posts on how the inverter and phase controller work to ensure no grid consumption. I have run an experiment whose results may lead to some other solutions.
while my controller is running using an oscilloscope with line trigger and a spare CT I have measured the current from the inverter and the current going to and from the grid.
the result is the inverter delivers current evenly over the whole mains cycle. this means that if the load from the immersion heater is phase controlled then the part of the mains cycle that it is on the current is drawn from the inverter and the grid if the inverter is not generating enough. On the part of the cycle that the crydom is off the inverter feeds into the grid. Over a cycle the net result is zero. the meter response time is more than a cycle and therefore does not record that you borrowed some power and gave it back before the end of the cycle. measuring the current going to and from the grid confirms the result. measuring the meters response time is more tricky as I would have to burst fire a SSR over an increasing time until the meter recorded if i get around to it I will post the results but I expect it will vary with meter type.
I shall be laying out a PCB ( currently on vero board ) and am happy to share the circuit diagram/component list/PCB layout with anybody who wants it.
incidentally I also ran the controller without the i/p filter and I am unable to Bluetooth to my inverter due to the interference showing that an input filter is absolutely essential.
the first solution used a PID controller crydom and true rms ct's which as people here have pointed out is a very expensive solution.
results
The true rms CT's are loaded by the PID controller this does not affect the operation but is undesirable.
the response time of the true rms cts is 300ms so the PID integration time had to be long
very small grid feed in with large load changes otherwise results good.
the second solution uses some inexpensive ops amps the crydom controller and a couple of owl ct's.
results
the cost is very low the owl ct's are obtainable for about £6 each op amps and other components are less than a £1. crydom is about £70 filter £25 power supply £10
response time is set at 100ms and no grid feed in or consumption is measurable.
As there has been many posts on how the inverter and phase controller work to ensure no grid consumption. I have run an experiment whose results may lead to some other solutions.
while my controller is running using an oscilloscope with line trigger and a spare CT I have measured the current from the inverter and the current going to and from the grid.
the result is the inverter delivers current evenly over the whole mains cycle. this means that if the load from the immersion heater is phase controlled then the part of the mains cycle that it is on the current is drawn from the inverter and the grid if the inverter is not generating enough. On the part of the cycle that the crydom is off the inverter feeds into the grid. Over a cycle the net result is zero. the meter response time is more than a cycle and therefore does not record that you borrowed some power and gave it back before the end of the cycle. measuring the current going to and from the grid confirms the result. measuring the meters response time is more tricky as I would have to burst fire a SSR over an increasing time until the meter recorded if i get around to it I will post the results but I expect it will vary with meter type.
I shall be laying out a PCB ( currently on vero board ) and am happy to share the circuit diagram/component list/PCB layout with anybody who wants it.
incidentally I also ran the controller without the i/p filter and I am unable to Bluetooth to my inverter due to the interference showing that an input filter is absolutely essential.
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