Hi,
I need a case to be waterproof and want to limit the amount of connectors.
I would like to have 1 2-pin connector that can both be used as output to drive a led and to be used as VCC input to charge the battery via a tp4056:
Is this doable? If yes could somebody give me a hint how?
Thx!
Jeroen
vorstendom:
I need a case to be waterproof and want to limit the amount of connectors.
Those are not mutually inclusive.
Plenty of waterproof cases around, just look in many of the big suppliers catalogues.
Depending on its actual use, if its waterproof rather than submersible, then a standard case with silicone sealer might do.
Again lots of waterproof/splash resistant connectors, heres one type on ebay ideal for motor applications etc.
Hi,
Case will be custom made (3d printed for now) as it will not be a standard form factor. It should be waterproof, no need to be submersible.
I want to limit the amount of holes (to reduce the chance of moisture coming in) therefore would like to use only 1 connector but I am unsure if this can be done electronically.
Thx for the connector tip, but it does not fit my purpose as it has no chassis/panel mount option.
Regards,
Jeroen
vorstendom:
Hi,
. It should be waterproof, no need to be submersible.
Are you aware that 3D printed cases are porous ?
@Boardburner
No this is new to me, I print PETG or ABS, both are very water resistant materials and used in many appliances. Do you have any reference for this?
There are lots of waterproof multipole IP66/67/68 panel mount connectors if you look in the big suppliers catalogues , though not cheap.
Why not just pass a cable out using a panel mount waterproof cable gland, much simpler.
I would say, if you switch to high side switching and put a diode from pin 1 of the connector to Vcc of the chip you're done. But keep in mind you have a diode drop so the voltage needs to be high enough.
But during charging you reverse bias the transistor. And depending on the applied voltage that might be out off spec....
@Ricky, cable glands is indeed an option and then use the waterproof connector type as you already mentioned. Only "but" is that it needs to be good looking casing and I find cable glands to be a bit bulky and uhhm ugly 
(unless you can point me to a neat one )
@Septillion, thx. I will try that. I am charging with 5V and have at least 3.7 from the battery so should be enough for the diode. Not sure about reverse bias the transistor. I use an IRLML2502. I checked the documentation but am not able te determine if it will be an issue.... Can you help me with that?
You can't use a single BJT transistor to switch current in both directions, you should add a shottky
diode between emitter and collector (anode to emitter) so the charging current can flow.
@MarkT, he doesn't want to. Yes, it's a bit unclear. But the input voltage doesn't need to go to the battery but to Vcc of the charger chip.
@vorstendom, if you use a mosfet, why draw a BJT? With a mosfet things change a bit because of the diode between drain and source... I don't know a solution from the top of my head...
Indeed I want to charge via VCC of the chip so that it is regulated.
ow **** very sorry septillion, I quickly drew up the schematic to paste an image in the topic... and indeed there is a mismatch in what I currently have in my proto and what I showed in the topic.
I started using mosfets because I had them lying around and these fully open with 3.7V on the gate, it should be no issue to switch to a regular transistor as I am not drawing that big a current (max 200mA).
I should use a PNP if using at high side right? Would a 2n5401 do? Will that fullly open and would that reverse bias be an issue? (appreciate the help! basic electronics I understand but having some troubles with these kind of details....)
vorstendom:
@BoardburnerNo this is new to me, I print PETG or ABS, both are very water resistant materials and used in many appliances. Do you have any reference for this?
It is not the fault of the material , the printing process itself leaves small holes.
There are some workarounds although most have to try several attempts to get it right.
Google should find comments on this.
Unless you have a need for a custom case i would suggest a commercial product will be a lot easier.
vorstendom:
I find cable glands to be a bit bulky and uhhm ugly
You could try mounting them inside out with suitable sealant
At the moment I'm a bit clueless how to fix this good. Then I should draw it and do some (ballpark) calculations... Will give it a try this evening (I hope...).
@Boardburner, hmmm gland inside out, that could be an option
Yeah, case is really custom, I have special mounting and shape requirements. But thanks for the heads-up. I will make sure I test it.
@Septillion, would realy appreciate it. Thx in advance!!
But on the other hand, how hard can it be to get a single 3-pole connector?
I need a case to be waterproof . . .
Better settle for 'water resistant'.
Any displays, switches, or cable entries, all bets are off.
.
Yes, 3-pole connector is also an option...
well... I will see how I am going to do it. Wireless charging is also an option, very neat but much more expensive.
Thx a lot for all the feedback!!!
If you already need a connector for a led(connector) then I would not bother with wireless charging.
I would just use a 3-pole connector and be done with it. No complex schematic etc. Just use high side switching and bring that out together with Vcc and GND.