- This topic is empty.
-
Posts
-
I soldered a 1.42u kit in the last couple days and I am not able to get it working. I did the initial testing across VIN and GND and got 5v and 3v on VCC so I proceeded to insert the remaining ICs and connect the lcd. Upon first power on the lcd is still dark (off). I also notice that the solder pins for usb connector are extremely hot to touch. I removed all ICs but MC34063 from sockets and rechecked voltage on VIN and VCC. Both now show 1.3v or 1.4v! I’ve double checked all my solder connections and been over the instructions again a couple of times but nothing seems obvious. Could I have damaged the IC? I don’t see any damage to resistors or capacitors. I’ve attached pictures here.
I also tested voltage on VIN and VCC powering with usb and voltages are even lower than with the orbit power supply.
Hi, I am on vacation this week and I will give you some quick troubleshooting suggestions to hopefully help you figure out the issue.
First, from the pictures, I couldn’t tell if the three pins of the power switch are soldered reliably. It looks like there isn’t much solder on those pins. So try to resolder these.
Seccond, if the voltages are wrong when the controller is powered by USB, that most likely means a shorting somewhere. You should measure the resistance between VIN and GND, also VCC and GND. They should be at least on kilo-ohm level. I won’t be surprised that yours shows only a few ohms.
The exact cause for shoring could be complicated. But I suggest that you first take off MC34063, measure the resistances again, and then if there is still shorting, desolder (or simply clip off) MCP1702-33 linear regulator. Let me know your discovery after following these steps.
VIN shows 002 resistance and VCC shows nothing (open?) when mc34063 both inserted or removed. Do you still want me to remove the linear regulator?
It looks like I will need to get more flux to fix the power switch. It just seems to ball up on the pins. Probably won’t have it till the end of the week. Thanks for getting back to me.
Yes you should remove the linear regulator because that’s connected to the VIN line and it’s very likely to have been damaged.
To solder reliably, you need to keep the soldering iron hot. Otherwise it may not reflow the solder well, causing fake solder joints. Normally fake solder joints won’t cause a big problem, but in some cases they will. For example, if the ‘Feedback’ pin of the switching regulator is not soldered well, it will cause the regulator to falsely sense that the output voltage has not yet reached the desired level, hence it will keep increasing the output voltage and that will potentially damage the components connected on the output line.
Resoldered power switch with flux and tested with mulitmeter.
linear regulator removed, no change.
I also removed the usb connector and replaced with a new one. No difference. My usb power supply light flashes when connected which means there is a short somewhere.
I removed the extra header I soldered to the VIN/VCC area and i think i’ve begun to damage some of the pcb traces. Copper is exposed in a few places. Posting picture.
My soldering iron is 60 watts, with a chisel tip. Plenty hot. Maybe too hot?
I’ve spent a great deal of time looking at my soldered connections with magnifier and nothing seems obvious. Anything I can check next?
I suspect that the problem is one of four things.
1. D3 is shorted
2. D2 is shorted
3. C2 is shorted
4. The PCB has a whisker or other etch problem between VIN and GND.My suggestion is to start by lifting one side of D3 and D2. To remove these components, you will need to get some solder wick to remove the solder from the leads. With one lead lifted in the air, check across this component is to see if it is shorted. Also check VIN to GND to see if that short ( low resistance) has gone away. After eliminating the diodes, the remove C2 and check across it for a short . Also, again check VIN to GND on the board. If the diodes and capacitor check OK, then I wonder if the PCB has a tiny whisker of tinning or copper that is shorting VIN to GND. The best way to find these is usually visual inspection under a microscope using a known good board. Given that you only have one board, use the best magnifying glass you have. Look for any connections, solder splashes or bent leads between GND which is that areas of the PCB that look like hatch or waffle pattern and VIN. Around C2, these areas get pretty close. Make sure to look at both sides of the PCB. You can also run a sharp needle point around solder pads in an attempt to break a whisker that you cannot easily see. The area of the PCB to concentrate on is that area that got hot when you powered it up.
The likelihood of D2 shorted is pretty small. D3 may be damaged because it’s a zener diode, and if the voltage presented on it is way above 5.1V it will be burned. So try to take off D3 first (just cut the leads from the front side of the PCB, you can always re-solder a new D3 back by soldering it from the front side of the PCB).
The likelihood of PCB trace problem is extremely small: all PCBs have been 100% tested. We use the same manufacturer for assembled OpenSprinkler boards and have not encountered any PCB trace problem so far.
Removed the zener diode. Testing it with my Horrible Freight multimeter shows .001 when testing it both directions so I am assuming that means its damaged. I now get 4.97v on the VIN but only 2.5v on VCC so I am assuming something else is likely damaged or its caused by the missing components. What should I do next?
I know, I need a new multimeter.
Thanks for your help so far!
2.5V Vcc means the MCP1702-33 linear regulator is probably damaged. You will have to replace it.
Also, was the 4.97V measured when it’s powered by USB or 24VAC? If by USB, there might still be a problem in your 24VAC -> 5V conversion (i.e. the switching regulator section) that caused the damage in the first place.
I am powering it by usb only so far. The linear regulator has already been removed (as well as zener diode). Do I still need to check D2 and C2?
I see, so the 2.5V you measured is not through the linear regulator. I assume once you have a working MCP1700-33 soldered, it should measure 3.3V.
If you need to purchase any components, you can either follow the part list to buy from Digikey, or I can send you any requested components at a small cost (just email me at [email protected])
I had a spare linear regulator on hand and now get 3.2v on VCC.
I don’t have a spare zener diode on hand but I can order from digikey. Is it possible to get it working without the zener diode still powering by usb? Obviously it won’t have 24vac to activate a solenoid…but maybe enough to get the ic’s/ethernet working?
During the build initially I tested vin and vcc with the correct voltages before adding the remainder of ics and lcd. After adding those the linear regulator and zener diode became damaged. Do you think there are any other spare components I should get from digikey?
The zener diode is optional (although it’s useful for over-voltage protection). You are right that USB power is sufficient to test the microcontroller and the web interface.
It’s very odd that your initial voltage testing passed but then components got damaged when other ICs and LCDs are plugged in. In any case, you can easily test if these components are still working by powering the controller through USB. The worst case is that the LCD and Ds1307 may be damaged (because they are connected to the +5V VIN line), but I assume the zener diode did protect them and hopefully they are fine.
It works via USB. I am able to view the interface with browser, which is very exciting.
I guess I still need help with the 24v side. The zener diode seems pretty important so I think I need a new one installed before doing much else. Do all the 24v conversion components needs to be replaced?
The zener diode, D3, is a crowbar. It is supposed to draw lots of current should the voltage rail exceed 5.6V. It will either blow any external fuse or give its life keeping the VCC (5V) rail from going too high. Be careful when purchasing a replacement. The voltage rating of the diode must be somewhat higher than the expected voltage. You cannot, for example, substitute a 5.1V zener.
I would suggest replacing D3 and then with UC1 removed, power the unit from USB and measure the voltage at pin 5 of IC1. This is the feedback voltage to the switching regulator. It must be at 1.25V. If this voltage is wrong, check resistors RT and RB.
Next, make sure that diodes D1 and D2 are not interchanged. These diodes have very different characteristics. Also make sure D2 is installed with the correct orientation.
Finally, replace IC1 and with USB disconnected apply 24V AC. Quickly check VIN (5V) and +3.3V, then power down and feel around for anything getting hot. If voltages are normal and everything is cool to the touch. Then give it a longer power up cycle. If still OK, then populate the rest of the ICs and LCD and do a full test.
Personally, I would not recommend plugging in 24 AC and the USB cable at the same time. Doing this connects the VIN of the OpenSprinkler with the +5V rail of the computer via the USB port. This may not be an issue on some computers. However, it could problems on others. This is because you could be tieing together the outputs of two different switching power supplies. Again, if the computer is well designed, it may not be an issue. The computer is supposed to have these ports current limited. The downstream device, here the OpenSprinkler, is supposed to be current limited too.
Agree with mrburns42.
My suspicion is that IC1 is probably damaged and should be replaced. D1 and D2 are unlikely to be damaged, but just to be sure, you can use your multimeter to measure the diode forward voltage on D1 and D2. D1 (R3000) should be somewhere around 0.8V to 1V. and D2 (1N5819) should be around 0.1 to 0.2V. If not, you should replace them as well.
D1 is showing 1.35volts, replace? D2 is .17volts. They are both installed correctly.
I have replacement components on the way should be here by Thurs. Glad I ordered some extra ones.
1.35V is ok for D1. Different multimeters will give different results. D1 is a diode with fairly high(up to 3V) forward voltage. So I think D1 is fine.
I replaced the zener diode and the switching regulator and It’s working now. I can’t tell you how those components became damaged unless one arrived doa… I can successfully turn on a solenoid with the web interface. I’ve not yet hooked it to an actual valve but I am sure it will work. Thank you so much for your help.
Thanks for the update, and glad to hear that it finally worked. Sorry that you had to go through the trouble. I also thought about the possibility of some parts being doa, but I don’t see any strong evidence. Before the SMT version became available, we have soldered and assembled 80+ DIY kits from the same batch of parts, and none of them had any issue. In many cases I’ve seen where the users report their build didn’t work, the soldering quality was a major issue. But from the pictures you’ve posted, your soldering seems to have good quality. So I am also curious what caused the problem in the first place.
- You must be logged in to reply to this topic.