Solar Power to Electricity: Around-the-year analysis

2017/03/04 Simon Leave a comment

Undoubtedly, a garden house will need most electric power in summer, because this is the time where you have long, worm evening. In winter, if you really want to stay in the garden house, better to switch the lights of and hibernate anyway.

So, how much yield (kWh) do you get from a photovoltaic system, located in Ludwigshafen, Germany? Well, there are very precise calculation models around, based on actual data. You only need to know the location, inclination and direction of the solar panel (and hope there is no shade!). For my location, about 8.4080 East, 49.4897 North, Orientation 192 degrees (SSW).

Then you go to Photovoltaic Estimation, and type in these numbers (select “stand-alone PV”).

Also, you need to know the Wp rating of the the photovoltaic cells. In the given case, we have 1 module “Siemens M55” (this has been around for a long time, datasheet of a current equivalent Siemens SM55 Datasheet), and a second one, quite similar, but slightly larger (need to find out the model number), all in all, 120 Wp estimated. The system also has lead acid batteries with total of 190 Ah capacity (C/100 discharge rate), but I just assume 170 Ah.

Feeding the various data into the calculator, it’s a really great tool!

Total energy that can be harvested, per day:

Now, lets be wasteful and consume an average of 400 Wh per day. That’s enough to run some lights, and a sizeable fridge all day.

A bit more conservative scenario, running an energy-efficient small fridge, and some lights (sure, you can also charge some cellphones or run a laptop computer).

Now, lets check if the battery will running low – just changed the discharge limit threshold to 20%.

Still good, seems like we will have plenty of electricity during summer the summer months – in winter, we will just switch off the fridge, anyway, it is the best time for hot rather than cold drinks.

Allotment 44

Standalone Photovoltaic System: lead acid energy storage cost

2017/03/04 Simon Leave a comment

For any standalone photovoltaic system, a battery is essential, because electricity is most needed when the sun is not shining. With all the many battery types around, lead acid type batteries still appear to be the best choice for a low-tech system in a harsh environment like a garden house.

First, we need to understand that the cycle life of lead acid batteries strongly depends on the degree of discharge (DOD) per cycle. I.e., a battery rated as “120 Ah” would be only discharged by x% of its total capacity, and last much longer than with a full discharge every cycle.

This is the battery we are talking about – quite impressive packaging, no wonder, because there is liquid sulfuric acid inside!

It is a N120S NRG Solar 12 V, 120 Ah, “Deep Cycle” battery. About EUR 75 if you buy it a the right spot.

Some average life cycle data vs. DOD% for lead acid batteries.

With cost, DOD%, etc, you can easily calculate the total energy stored over the cycle life of the battery. Time-wise, the battery can last about 8 years, at least according to the manufacturer’s data. So, with about 100 cycles maximum per year, one cycle per day (unless earth rotation will pick up dramatically…), no particular useful life beyond 800 cycles.

With these data, it is quite clear that for the type of battery brand I am using (which is not the best most expensive super grade solar battery), running at 20~40% DOD will give quite OK life time expectancy, and cost even lower than domestic/grid power here in Germany, at least with the paid-off solar cells and charger.

Sure, measures will need to be taken to avoid full discharge of the battery in winter, e.g., by disconnecting all major consumers, and just allow for some LED or fluorescent lights, and maybe, a few cellphone chargers.

Allotment 44

Allotment 44 (Parzelle 44): Gardening, rather than soldering!

2017/03/04 Simon Leave a comment

In these days of global trade, endless supply, and magnificent business opportunities, why not take a step back, and spend some time preparing the ground, in the the literal sense. This time of the year is great for such activities, and after several months of winter, working outside in the fresh air is certainly a recipe to keep good health and to enjoy life with family and friends.

Long story short, after passing the formal application procedure and test, we are now the proud owners of a garden allotment, number 44. In German, Parzelle 44 (Kleingartenanlage am Riedsaumpark, Ludwigshafen am Rhein, Germany).

The last owner could not maintain it for the last 2 years, so, it is in a bit desolate state, but nothing that can’t be fixed, and with these pictures being a few days old, it is now looking already much better.

This a general view of the allotment, 300 square meters total, a bit over 3200 square feet.

It also features several buildings: a garden house (stone-built, dry, and in good shape, just needs a bit of paint), a summer kitchen and workshop (wood frame construction, behind the house), and a tool shed (other side of the house), as well as a rather spacious patio. Enough space to stay there over the weekend, or to have extensive BBQ with a whole soccer team.

Needless to say, it is a garden house, there is no connection to the power grid, or to a gas pipeline – at least, we have tap water! All else will need to be served by propane bottles, and by a photovoltaic system. Sure enough, no need to upgrade this to a too high level, with the main residence just a 10 minutes walk away, and we don’t want to defeat the purpose of it, to be a bit close to nature!

Stay posted!

Miscellaneous

Cast Aluminium Wok with Gas Burner: a 10.5 kW cooking arrangement

2017/02/08 Simon Leave a comment

With frequent trips to Asia (almost half-time living there at the moment), I don’t really get sick of Asian food. Even more so, if we can all it European style food, cooked in a wok. All fresh vegetables, some meet, some fried rice, cooking limited to a few minutes, and not a lot of dishes to wash up afterwards.

This is the arrangement. The wok, from Thailand, is cast aluminium, and very good for all kinds of wok cooking styles, including stir fry, fried rice, deep fry, steam cooking, and so on.

The real key to wok cooking is not so much the wok itself, which comes in various types of materials (never take anything that is coated, either black steel, cast iron, or aluminium give the best result). The real key is the burner, and its power. Unless, if you have a really strong custom build induction coil heater… more about his later.

The burner, it is propane fired, and comes in an easy to assemble set of parts, for about EUR 40, delivered. Great value.

See the data. The power is pretty good, and can be regulated down a bit if needed. But most times, I use this thing full power, along with a 5 kg propane bottle, which seems to last for a while.

Before you use a new wok, be sure to clean it properly, and then burn-in by using some vegetable oil (heat resistant, don’t use olive oil). With some paper towel, and a wooden stick, wipe the wok inner surface, while it is really hot, and until some brown layer is forming. This should all be done on outside, and only use a small amount of oil, and never hold your head anywhere close to the wok, because the fumes may catch fire any time. At my end, everything worked out nicely and quietly, but not without the smell or burning hot vegetable oil.

After cool down, time for some first dish. This is not a cooking block, sure you will find your own recipes.

Cleaning is easily accomplished with hot water and a very minor amount of a mild cleaning agent. If at all possible, just wipe out and clean with water, no cleaning agent, and use daily, to preserve the anti-stick properties of the surface.

Various

Dual CV 1600 Stereo Amplifier: a real HiFi classic with some capacitor smoke, and a very large dropout voltage regulator

2017/02/08 Simon 1 Comment

This one is a real gem, a stereo amplifier, Made in Germany, and nicely constructed in the 1970s, using mostly discrete parts.

Some issues are common to all old amplifier, like, defective switches, aged contacts, and so on, but these can be fixed with good contact spray, or by (mechanical) repairs. For the CV 1600, most common fault is the X2 mains capacitor, 47 nF, which will eventually turn into smoke and stench. Be sure to replace this part, if you have a CV 1600.

The 47 nF X2 rated cap is located on a fuse board, and to get access, you need to remove all the transistor wires. This is best done with great care, and without damaging the wires, otherwise, it is quite laborious to connect everything back up again.

This CV 1600 also had another issue, no signal from the distribution amplifier board. Some first check showed issues with the +15 V rail being stuck at ~7V. Probably a defective Tantalum or other capacitor? Probably not – not much current flowing either, so it is not related to a short at the output.

Inspecting the regulator – it is a TO-202 LM341p15, pretty rare nowadays.

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No heatsink on the regulator, so I got a bit worried with the dissipation of TO-202 vs. TO-220 devices – all I have in stock are TO-220 regulators, LM78xx series.

After inspection of the datasheets – nothing to worry about. Pretty similar heat resistance, junction to ambient. Voltage drop is about 10 V, current roughly 50 mA, so, 0.5 W – roughly 30 K temperature rise.

A quick test with a 5.6 Ohms, 250 W dummy load showed no further issues (except an incorrectly installed signal cable, probably from an earlier attempt of someone else to fix this unit?).

Finally, some performance data of the CV 1600.

Miscellaneous

Really Hot: Brick Oven Pizza at Home

2017/01/28 Simon Leave a comment

To prepare a brick oven pizza, no doubt, the most suitable apparatus would be a brick oven, wood fired. However, it is hard to come by at your home, and not quite viable to heat up such massive equipment just for one or two pizzas.
Time to try out a present received for xmas, a brick, which fits my oven very well. The material is Schamotte, a Mullite-type Si-Al-Oxide material. Make sure to get a food grade stone, because many refractory bricks intended for industrial use contain heavy metals, and this is not what we want for the pizza.

For the dough, there are a few things to consider. It can’t be too soft, otherwise, it will be difficult to handle. Some good recipes:

Basic Recipe

500 g wheat flour (unbleached, German type 405)
–> can be substituted by a mixture of 150 g of whole wheat flour, and 350 g of wheat flour.
15 g of salt
3 spoons of vegetable oil
1 spoon of sugar
270 ml warm water
10 g of yeast, or sufficient active dry yeast

To prepare the dough, dissolve yeast and sugar in water, and add salt, oil, and about 3/4 of the flour. Mix thoroughly, add remaining flour, mix, and knead with your hands until the dough is nice and firm.
Let rise for 1-2 hours, or longer, depending on temperature.

Form into round pieces, about 100 g each for small size pizza, and let these pieces rest for about 35-45 minutes.

Above, this is what it should look like.

Then, roll out the pieces, without any further kneading, and use some flour and semolina as an anti-stick agent.

Make sure the stone is pre-heated at full power, 250°C temperature.

Put the pizza on a wooden panel of appropriate size to move it around, and slide it on the stone. Don’t add too much sauce, otherwise, the pizza might get stuck to the stone.

MMMMMMHHhhhh delicious!

Needless to say, there are many uses for the pizza stone, like, baking bread rolls, onion breads, or flat breads. A great opportunity for some experimentation!

Various

HP 6115A Precision Power Supply: repair complete!

2016/12/18 Simon Leave a comment

No repair can proceed, without sufficient time, and without the right spare parts. Time was very much occupied by other business recently, spares took time to ship from Greece to Germany… the 2N6211 transistors.

Here they are – the 2N3442 are China-made (ISC) transistors of rather recent production, the 2N6211 date back to 1992.
Not much to write about the further repair, mounted the transistors on the heat sink, soldered-on the cables, replaced the Zener diodes of the main board (series regulator bias), and switched the 6115A on. Success! Some minor calibration of the panel meter. Other than that, all in good shape.

Various things can be measured to verify the correct operation of the 6115A, here just a quick test checking all the ranges, linearity, and deviations. In short, it is very much more accurate than the 0.025% + 1 mV output accuracy specification.

After a full cool-down, checked the stability/drift after a cold start, with the output programmed to 10 volts. It is ramping up nicely, with some very minor “instability” during the first hour, but then stabilizing to almost perfect level. This is with no load. Sure it may degrade a bit under full load, fair enough (horizontal axis shows measurement number, period is about 0.3 s per measurement).

Finally, this is the working precision supply.

Various

HP 6115A Precision Power Supply: not just one defect mixed with a lot of precision

2016/11/23 Simon Leave a comment

The HP 6115A is a really great power supply, 0-50 V @0.8 Amp, 50-100 V @0.4 Amp, 0.0005% load and line regulation, 0.01% current regulation, 100 uV p-p ripple, 0.0015% drift over 8 hours, 0.025 + 1 mV accuaracy of output voltage, all in all, challenging design objectives still today. Unfortunately, the unit discussed here has not any of these characteristics, it is dead, and missing the current adjustment pot.

At least, it is a reasonable clean unit, and at a first glance, nothing major, like a completely melted board or smoking transformer. Judging from the soldering, someone already tried to fix it but gave up mid-way. Sure, I will not give up with this supply too soon.

First things first – the current pot, a 10 turn 1 k, HP part 2100-1864 (Bourns 3540S): missing. Looking around in my parts collection – but no luck. At the very bottom of a stack of old electronics junk, a WTW 610 pH meter from the 1970s. This is used to convert pH electrode signals, to proper voltages, but even more important, it has 2 pcs 1k Helipot 7276 series 1 k pots. These are 20 ppm tempco, even better than the Bourns (50 ppm).

With the 1 kOhm pot fitted, still no function. About 60 V at the output, and the current limit LED lit, regardless of current or voltage setting.

Looking around inside – a few issues found. There are several uncommon parts, like, a STB523 = 1N4830 voltage stabilizer, which is more or less a stack of 3 Si diodes. These parts are not commonly available anymore, so I replaced the defect regulator diode with a series assembly of three 1N4148 diodes.

Found a few more issues, several blown Zener diodes, all around the Q1-Q4 transistors. This is not good, because it may indicate some blown power transistors. And if fact, it did not take long to find out that Q1 has a full B-E-C short, and Q4 is C-B short, E-C, E-B open. No wonder that this disturbed the bias network Zeners, VR3, VR4.

The transistors, 2N3442 NPN (Q1-Q3), and 2N6211 (PNP, high voltage power TO-66), at least the latter, not quite common – on order from an xbay seller in Greece, 5 EUR a piece of old and obsolete part, OK!
The power transistor board was an awful mix of bad soldering and flux, finally, cleaned and most of the solder removed.

Found another defect – no voltage on C8, one of the main capacitors. Reason: a blown trace, from tap 16 of the transformer. Temporary fix with a yellow wire….

After some repairs, at least the basic voltages and supplies are up and working again, all capacitors tested, and working fine. Also reviewed the regulator board and its voltages (not shown in below diagram, red cross means dead part removed, green cross means part absent but tested good), all is fine and working.

Note the working principle of the series pass regulator – it is a dual range setup, with a high voltage regulator, Q1 and the low voltage regulator Q2/Q3, all driven by the common Q4. Diodes CR11 and CR12 (a dual-diode element) is directing the current from the appropriate transformer DC supply (2 equal DC voltages of about 80 Volts are generated from two separate windings).

Apart from a 1N829 0.0005% tempco temperature compensate diode, there is another remarkable part used in the circuit, a 10 ppm 10 turn trimmer – not quite cheap, and still available today!

This is the current state of the instrument, waiting for the spare transistors, before I can put it back together, and hopefully, put it back in service.

Micro-Tel MSR-902C

Micro-Tel MSR-902C Receiver: root cause analysis, and a volt meter

2016/11/02 Simon Leave a comment

Finally, some time to deal with the MSR-902C repairs. After replacing the 7401 TTL, and a 7404 TTL, the band select logic seems to work well, except two bands. This could be traced to a dead transistor on the A3A5 band control board. Still a mystery, what caused all these defects? Tracing the line going to the dead transistor (which appears to be a simple +15 V on/off switch), it only goes to one place – a circuit far inside the receiver. As it turns out, this is a hand-wired circuit, not really a circuit board, but a piece of sheet metal with various solder posts. And, on the other side, two filter. One filter mounted properly, the other tied to it with some thread. As you can see, this holds the filter in place, but it can still move around the other filter – and cause a short on the 15 V rail, including the signal coming from the transistor switch.

To avoid similar defects in the future, I put some plastic sheet around the filter, and fixed it in place with better ties.

Finally, time for some alignment of the YIG filter, by using a fairly complex setup, a microwave signal generator, a scope to test the receiver output, etc. – see below picture.

The YIG filter needs to be aligned for each band, same for the YTO band edge frequencies. This is all done on the A3B7 board. Not much adjustment needed, fortunately, only some fine tuning of the YIG preselectors.

Receiving… quite fun to operate the receiver, easy to tune over the full range of frequencies. Maybe this is what makes it so suitable for detecting microwave bugs.

Some last repair relates to the frequency display. It did work in some bands originally, not sure how the defect came about – maybe I slipped with a screwdriver, or some other mishap, or some already damaged part, I can’t tell. But now it only shows erratic values, and without a schematic, it is a tough task to fix it.

A fairly complex assembly, keep it mind, it is just a volt meter for the frequency display… so much easier nowadays…

The LED display: hand-wired with Teflon coated wires. Sure, this receiver was never intended for the layman, but for some agencies that don’t care about cost and taxpayers’ money.

After some tests and checks – the voltmeter uses a voltage to frequency/time converter, and a MIC5005 integrated timer! Quite a nice and complex chip for its age!

Two hours later – found the issue. A bad reference diode, 1n821. Unfortunately, no such diode in stock, but it is quite similar to the 1n827, only that the latter is more precise, and more expensive, and only a used part in my bin. But easy to check, just put a resistor in series, and run at about 1 mA, and check the voltage drop over the diode. All good.

Finally, reception is pretty good over all bands, no detail tests of noise levels done yet, but already now it is clear that this is pretty capable receiver, build with only the best components at a time – just the style is not quite service friendly.

Demodulators work as well, receiving 1 kHz demodulated signal, all looking pretty good and clean.

Miscellaneous

Phillips Senseo Coffee Brewing System: the serious consequences of a broken wire

2016/10/31 Simon 1 Comment

With close to 40 million sets sold, the Phillips Senseo coffee makers are in widespread use in various parts of the world, predominantly, Europe. Also at my workshop, this machine provides the essential supply of coffee. However, recently, this supply came to a sudden and unexpected hold, leaving me in a serious situation – stuck without coffee.

The defect was not related to any of the electronic or electric parts, but to the closing mechanism of the head part. It just would not close properly.

First we need to have a look inside. Using a screwdriver, the lid can be easily disassembled, by prying out the inner part with a screwdriver (needs to be done left and right).

Inside, a broken wire spring, which is 1.5 mm in diameter, and made from some rather stiff stainless steel spring wire.

Where to get a spare wire? No 1.5 mm spring wire around here, but an old egg beater (maybe you can use some steel wires of an old umbrella?). So I decided to sacrifice one of its wires to the coffee machine repair.

Here, you can see the wire installed. It is not quite 1.5 mm thick, but still, it works.

After this quick fix, coffee again!

SimonsDialogs

Solar Power to Electricity: Around-the-year analysis

Standalone Photovoltaic System: lead acid energy storage cost

Allotment 44 (Parzelle 44): Gardening, rather than soldering!

Cast Aluminium Wok with Gas Burner: a 10.5 kW cooking arrangement

Dual CV 1600 Stereo Amplifier: a real HiFi classic with some capacitor smoke, and a very large dropout voltage regulator

Really Hot: Brick Oven Pizza at Home

HP 6115A Precision Power Supply: repair complete!

HP 6115A Precision Power Supply: not just one defect mixed with a lot of precision

Micro-Tel MSR-902C Receiver: root cause analysis, and a volt meter

Phillips Senseo Coffee Brewing System: the serious consequences of a broken wire

SimonsDialogs – A wild collection of random thoughts, observations and learnings. Presented by Simon.