I see the difference between series and parallel now. But I can't see it being practical to have more than 2 resistors for this. I know circuit boards can have well over 100 resistors in them, but for my situation, shouldn't I have just one resistor that can handle it?

 

Also I have a 68ohm 1/2 watt resistor that gets warm when device is off but not hot hot when connected to battery. But that resistor gets really hot when I connect to 5v and device is off.

That's unusual. Almost sounds like you have a short to ground somewhere. Anyway, try four 270 ohm resistors in parallel. That should fix the overheating issue.

 

I see the difference between series and parallel now. But I can't see it being practical to have more than 2 resistors for this. I know circuit boards can have well over 100 resistors in them, but for my situation, shouldn't I have just one resistor that can handle it?

Sure, you just need a high enough power rating. The resistors-in-parallel trick is just useful for reducing the overall wattage going through any single resistor.

 

Tell us what you're expecting the resistors to do. If you want to reduce voltage, that's not the way it's normally done.

 

That's unusual. Almost sounds like you have a short to ground somewhere. Anyway, try four 270 ohm resistors in parallel. That should fix the overheating issue.

Should they each be of 2 watts?

 

Should they each be of 2 watts?

No, just standard 1/4 watt resistors. 5V / 68ohms = ~73.5ma, so you have about 367mw to dissipate. Using four 270 ohm resistors in parallel gives you 67.5 ohms (which is close enough to 68 for low voltage circuits) and 74ma of current and so 370mw/4 = ~92.5mw of power through each resistor.

 

Tell us what you're expecting the resistors to do. If you want to reduce voltage, that's not the way it's normally done.

The li-poly will always be connected to the powerbooster. The powerbooster supplies 2 methods of power to the protrinket and, the protrinket sends signals to the motor board upon detecting signals from the ir leds.
Now because I have burned many powerboosters trying to fix this, I thought that the only way to cut power to the components from the powerbooster was to add a resistor. I need to cut complete power when the device is off so I don't drain the battery that is always connected to it.

If there is a better way to cut power I am eager to try it out. Otherwise, I think I will try XOX's suggestion.

Thank you all for your help. I will try to get back to this post after I trial this method.

Took time to post the reply, cause I reached the post limit in one hour.

 

If there is a better way to cut power I am eager to try it out.

You have power sources of 5V or 3.7V. What voltages do all of the devices you're using require?

BTW, you shouldn't connect a 5V source across the battery. You need to use a proper charging circuit or the battery could cause a fire.

 

I think I would read there page
https://learn.adafruit.com/adafruit-powerboost-1000c-load-share-usb-charge-boost/pinouts

 

Okay, so I have come to the conclusion that I can't easily accommodate for both the 3.7v li-poly battery and the 5v power plug.

I connected a voltage regulator (dl234, not sure if that's what you meant) to the li-poly battery to output 5v to match the main power plug source from the micro-usb. This way I was able to add 3x 13 ohm 2 watt resistors (the only ones that worked on hand out of many I had).

It works where none of the components get hot and burn out, but the resistors are pretty warm. They don't get hot hot to the point where I have to remove my finger. I have yet to get the 4x 270 ohm 1/4 watt resistors and try those. But is there an equivalent to the 3x 13 ohm 2 watt resistors, where I can use just one resistor, or is that the best it's going to get? I thought of a 39 ohm 2 watt resistor, but am not sure if it will work the same way. I placed an order for them.

Be80be, I have this source for the powerbooster. I went through it again, but I doubt I missed anything??? Thanks though

 

An actual schematic would be AMAZING here.

 

Actually I don't have a question on my schematic. I would like to know if there is an equivalence to [3x] 13 ohm 2 watt resistors, to use just one? Like 39 ohm 2 watt?

 

Actually I don't have a question on my schematic. I would like to know if there is an equivalence to [3x] 13 ohm 2 watt resistors, to use just one? Like 39 ohm 2 watt?

If the resistors are in series, you could make the substitution you mentioned.

But, you've been putting them in parallel. The equivalent single resistor for 3 13 ohm 2W in parallel would be a 4.3 ohm 6W resistor.

Resistances in series add.

 

No I tried parallel, but I have been putting them in series. But thanks for seconding my suggestion. I'll try it out when I receive them.

 

The purpose of the resistor is to make the powerboost 1000c work correctly the way I need it to. It is wired with ENable pin to ground, so that when device is off, the powerboost does not turn on and waste charge from battery.

You should really consider sharing a schematic showing what you're doing with these resistors. I'd bet almost anything that there's a cheaper, easier way to accomplish whatever you're trying to accomplish, instead of running low resistance, high wattage resistors.

You say you don't want to "waste" charge from the battery, but if you're making resistors too hot to touch when your device is "off," you're wasting HUGE amounts of energy.

If you can more clearly describe what you're trying to do with these resistors, and if you can show how you're currently connecting them, we can probably find you a better solution.

 

Your right. But the schematic was already uploaded on the first page of this forum. I drew as best as I could. It doesn't have the 3x new resistors drawn in them, because I am working on figuring out what I need and how to do it. I explained everything earlier in this forum.

 

Your right. But the schematic was already uploaded on the first page of this forum. I drew as best as I could. It doesn't have the 3x new resistors drawn in them, because I am working on figuring out what I need and how to do it. I explained everything earlier in this forum.

Yes, I know, but your explanation of what you're trying to do with the resistors makes no sense to me. Either I'm totally misunderstanding you, or you've totally gone down a dead-end path.

EDIT: Ok, I see what's going on now (despite your unwillingness to share current schematics or rephrase your verbal explanations.) You've connected the power boost and the battery all wrong. Before you buy any more resistors, destroy any more boost boards, or start a fire, check out the Adafruit link @be80be shared above.

I have to get to work now, but if you can't figure out how to rewire things I'm sure someone here will help (if no one else does, I can try this evening after work.) Hint: according to the Adafruit pin descriptions, your battery, your power supply, and your load (the rest of your circuit) should all connect directly to the power boost, NOT to each other. Get this right and you won't need giant, burning hot resistors.

 

Thank you for that, but I am not even sure I drew the schematic correct. What I can do is upload some photos of the components and try to elaborate on how they are wired and what they do.

I originally wired it where nothing would overheat and these resistors were not needed. (Now as I am riding the train to work, I realize that I may have wired it correctly the first time). Well, before the charging and charged led indicators didn't work correctly. So I didn't know when battery was charged. It kept saying charging with orange light. So I rewired them where I saw the light working correctly, but the powerbooster would overheat.

I think maybe the board was faulty...as I have gone through several. I will try to explain with pics when I get home tonight.

 

Thank you for that, but I am not even sure I drew the schematic correct. What I can do is upload some photos of the components and try to elaborate on how they are wired and what they do.

I originally wired it where nothing would overheat and these resistors were not needed. (Now as I am riding the train to work, I realize that I may have wired it correctly the first time). Well, before the charging and charged led indicators didn't work correctly. So I didn't know when battery was charged. It kept saying charging with orange light. So I rewired them where I saw the light working correctly, but the powerbooster would overheat.

I think maybe the board was faulty...as I have gone through several. I will try to explain with pics when I get home tonight.

If schematics are too confusing, how about this picture from the Adafruit website (with some extra notes.)



*** Notice that the power supply and the battery only connect to the power boost board, not to the rest of the circuit. Also note that the "5V" pin absolutely does not connect to the battery in any way. That pin is the boosted output from the board - it's for powering your circuit.

 

I tried without the resistors, but I can't seem to figure it out. Many of you have me advice, but when trying without, my powerbooster would heat up somewhere. And the powerbooster is fine. I used a new one to see if any difference.

So I played it safe using resistors and voltage regulator for now. Hope the picture or readable. The resistors are in series. And the sensors are hidden underneath, because they react to light.