PS For future reference, does this sort of exposed PCB trace (pad?) used for electrical connection take solder well?
I can’t tell if you have gold plate or just raw copper (probably gold. But in either case, yes, it is solderable. You can think a little bit about how they manufacture the boards. First the print on the green solder resist, then they dunk it into an electroplating bath for a gold finish, or a dunk it in solder for HASL. It would be a lot of trouble to go through (=$$$) to individually mask off that part of the board for some special process.
In addition to the voltages being different between real-RS232 and "TTL"-serial, they're also swapped. On a DB9 you probably have something approximating RS232, where mark=-9V and space=+9V, but the debug header is likely mark=+3V and space=0V. So even if your inputs can handle a wide voltage range, the sense is inverted, which is why you'll get garble.
(For example, when the line is idle it's at the 'mark' voltage and the receiver knows a character is incoming when it transitions to 'space' for one period (the start-bit). If mark and space are swapped, the receiver will see 'space' most of the time and only detect a character starting when there are some 'mark' bits in the middle of a transmitted character. It'll never actually synchronize correctly with the transmitter.)
You can figure out what you've got with a multimeter and checking what the voltage is on the TX pin when it's idle.
I'd assume that since it's from a thermostat, it's likely a custom made part - most of the common traditional thermostat companies like have been around for a while tend to mostly reuse their existing custom designs instead of using standardised components
Since it's peeling this could be difficult to salvage too... usually I use foil to solve connection issues caused by corrosion, or have a poke around on Ebay for a secondhand one if it's really bad
You could also consider re-shaping a (conductive) paperclip to contact the aa battery in a similar way.
I've had middling-to-good results making battery contacts out of springy bronze metal stock. It solders well, it's easy to shape, and if you get the right kind of metal it retains its springiness well. (510 or 544 alloy, maybe? It's been a while.)
It’s similar to AC-DC. From a simplistic perspective, efficiency at idle will be 0% because the converter itself still uses some power, then efficiency increases with load since the converter overhead becomes less significant as the useful work increases. Googling “dc dc converter efficiency curve” gives plenty of results.
They might be willing to spec it as "quiescent current" (current drawn at 0 load) even if they don't provide a full curve. Annoying that it's not on the datasheet.
Second picture: To me looks like Q1 (3400) is an NMOS which connects the LEDs to power. The ‘gate’ is marked yellow. It is the ‘control’ input of the MOSFET. The 4 resistors RD RC RB RA (purple) probably limit the current through the LEDs. If you’re lucky, then an easy hack would be to bypass this transistor: Remove Q1 and connect the red and green marks via a mechanical switch. You’d need to scratch away the white coating until you get copper. Then solder wires there. As a consistency check you could measure the voltage over Q1 (red and green marks). Measure once when the module is plugged in but switched off, and once when the LEDs light up. If you see a voltage while the LEDs are dark, then this would partially confirm my guess. As a test: Before removing Q1 you could also try to bypass Q1 with a resistor (~ one, two kOhm) while the LEDs are off. If you see LEDs now lighting dimm, you know that Q1 is the one switching the LEDs.
Other possibility: It might possible that the timeout is computed with an R-C circuit. for 30min you need a rather large resistor because there can’t be very big transistors. R1 (blue) is the largest one. Experiment could be to remove it and see if timeout is still 30min. Or put another 10k resistor in series and see if the timeout gets shorter.
Wondering: What voltage do you connect to the module? Please be extra careful if you have somewhere mains supply voltage.
If you mean a replacement slide-in US standard module - I fear that your chances are slim. I don’t know of a standard that applies to such plates. As it came with a, presumably, external disc drive - asking that manufacturer or its US agent/distributor for help might get something. Even a free replacement power supply. Worth asking, surely?
I don’t recommend using an inline adapter - unless used vertically, the leverage would be too great, unless you added a third leg… You might look for a right angle adapter - that’s the norm in the UK. They can work out well.
Otherwise, you could get an EU socket strip, replacing the plug on the end of its cable with a US one (if it doesn’t actually come with a US plug already).
'fraid that a little bit of effort producing the circuit diagram from the boards is really needed.
I think that it will show what has to be a microcontroller with an input pad going to the switch and another pad going to a base resistor for q1. Q1 switching power to LEDS via RA - D.
The long light looks to be fitted for a an IR receiver. With U1 near it possibly the decoder. As they show the thing stuck on a rafter presumably way out of reach - I suspect that 's a picture from the version with an IR controller. They have produced a cheaper version, without the sensor and re-used the photos.
Now, if that’s how it is - I’d just remove the microcontroller and glue one of my favs upside down on the board and run wires from its pins to the relevant pads (removing the existing microcontroller). I haven’t bought one recently, but 8 pin ones were costing me less than 50p… Having programmed the replacement with an added option to stay on.
We have a council-supported “man cave” - with a couple of funded workshop technicians and lots of unpaid volunteer specialist engineers, mechanics, DIY’ers etc. Plus a very well equipped multi-discipline workshop. So you could take those bits of kit there and someone would give you a hand setting them up, teaching you how to use them, repairing them/maintaining them as needed. Even getting them calibration certificates (thanks to one of the volunteers who has access to calibration equipment). If you don’t have one locally - wouldn’t the technician at a local school/college/university help? Is there a local community online group that you could join and ask for help?
Yes you can absolutely breadboard it. Forcing a current is as easy as following ohm’s law. Make sure there is a certain voltage across a resistor and ensure that only a negligible amount of that current is leaked elsewhere. A difference amplifier is a good way to ensure this, as long as you pay attention to the amplifier input currents.
If current regulation isn’t super important, a highish voltage (say 24+ V) and a large resistor will also work because the variation of threshold voltage will be so small that the voltage across the resistor will be relatively stable.
I think there is some confusion about the word diode here. The transistor is effectively an inverting amplifier, that is that the drain voltage is reduced if the gate voltage is increased. By tying them together, they reach a stable configuration where the gate is just high enough to make the drain low enough for them to be equal. In this configuration, there are two terminals, hence the di in diode. Like a traditional diode, it has a very nonlinear voltage-current relationship. If you apply 10V to it, theoretically the current would be thousands of amperes. Practically that won’t happen but you will blow up the transistor.
I don’t know enough about radiation and semiconductor physics to answer your other questions but if I were you I would just build it and test it. MOSFETs and resistors are cheap and if you do have a radiating source on hand it might be easier to try and fail than to hope someone here can tell you what your part will do when exposed to conditions outside of the manufacturer recommendations.
For the first one: Would be good to know what U1 is exactly. Can you read any number/code on it?
If you are lucky it is simply a ‘switch’ which switches on once you press the button and switches of after 30min. In this case you could add a wire which constantly switches the lights on. Then add a normal mechanical switch to the power supply cables.
If you are unlucky, U1 also regulates the current through the LEDs. Then cannot be easily replaced. Is there anything on the other side?
First image: U1 says HZ300 0053, and Q1 says 3400A. The second image has two U1 components: the smaller says RCAKL9 00765, the larger is 6228A 2121/33, and the Q1 is 3400X. There’s nothing on the back of the board.
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