5v box mod question

[gratefulme]

OK I built this using a rat shack LM7805c. For some reason I can't get 5v coming out of the resistor. Coming in I get 7.7v coming out I only get 2.7v. I have no idea why. Everything seems to be wired right. Can someone think of a reason for this? It won't run the atty at all. The weird thing is it was working before charging the batteries. It it possible it is to much voltage to the chip?

 

[Guitarslinger]

Hmmm-no picture or schematic does complicate things (at least I can't seem to see one.)

 

[gratefulme]

Here's a pic

pos to switch, Switch out to left pin, right pin to atty center,middle pin to addy edge and neg battery.

 

[Ez Duzit]

Data sheet for LM7805c shows 10v input with 5v output, and also says you need Min 7.5v input to maintain line regulation. That's cutting it close. You're better off with the Texas Instruments part. It has perfect specs for an ecig. In fact if you register with TI.com, they will send you up to 5 samples of this part totally free, they even cover shipping.

Data Sheet for LM7805c
http://www.datasheetcatalog.org/datasheet/nationalsemiconductor/DS007746.PDF

TI.com samples (Scroll to top of page for part specs)
Linear Regulators - Single Channel LDO - UCC383-5 - TI.com

 

[gratefulme]

I understand the ti part is better, but I don't have any right now (hopefully be here today.) Is this part not going to work? I just don't understand why it would work before I charged the batteries, but not now.

 

[cpcp68]

the 7805 will not work as the battery voltage is too close to the minimum it takes. you need a regulator that belongs to the family of the low-dropout regulators. A good part would be National's LP38690 or the TI Ez suggested

 

[cpcp68]

oh, I forgot. be careful; sometimes LDOs require a ceramic cap ~1uF at the output to be stable. It is always a good idea to put some C at the input and output of regulators.

 

[gratefulme]

OK I got the ti regulator in here it is installed same way, same problem. Any ideas?

 

[cpcp68]

possible causes: wiring- check carefully
make sure the metallic fin of the package does not contact anything (it can be in contact with the negative)
atty shorted?
is the input voltage to the regulator actually there?

 

[gratefulme]

To be honest I'm using a cheap harbor freight multi so I'm not sure on the voltage but it seems to be there the numbers are just weird. this morning they seemed right but not now. If I put pos prob in center hole and neg against side I get plenty of power more than 5v. I'm not sure why except it is a cheap multi. So why doesn't it power up, the atty works in a 510 battery so I know its not the prob. And yes I have checked, no wires touching anything except what the are soldered to.

 

[opuscroakus]

To be honest I'm using a cheap harbor freight multi so I'm not sure on the voltage but it seems to be there the numbers are just weird. this morning they seemed right but not now. If I put pos prob in center hole and neg against side I get plenty of power more than 5v. I'm not sure why except it is a cheap multi. So why doesn't it power up, the atty works in a 510 battery so I know its not the prob. And yes I have checked, no wires touching anything except what the are soldered to.

Are you getting 5v at the atty connector? If you are, connect the atty, attach the probes to the atty connector, press the button and check the volts. That should give you a better idea of the volts under load. I would also check to make sure the atty is making a good connection in the atty connector.

 

[NickJuice]

To be honest I'm using a cheap harbor freight multi so I'm not sure on the voltage but it seems to be there the numbers are just weird. this morning they seemed right but not now. If I put pos prob in center hole and neg against side I get plenty of power more than 5v. I'm not sure why except it is a cheap multi. So why doesn't it power up, the atty works in a 510 battery so I know its not the prob. And yes I have checked, no wires touching anything except what the are soldered to.

My best bet? You've got a bad battery...sounds like your getting over 5v unloaded but when you put a load on it...it drops to 2.7? Sounds like a bad battery that can't handle the load..what batteries are you using? do you have another mod you can test them one at a time in?

 

[gratefulme]

I'm testing from the inside of the box I hope that is what you mean. When I test without the atty I get 5.8v. The difference I believe is the cheap meter. BUT with the atty atached I get nothing. Not sure why.

 

[gratefulme]

I'm using the trustfires in the pics. I don't have anymore nor any way to check them bummer.

 

[gratefulme]

Well I put them both in the charger one at a time. One stayed green, while the other went red. Maybe one side of my charger doesn't work, and it never got charged. I'll report back when the light goes green.

 

[opuscroakus]

Well I put them both in the charger one at a time. One stayed green, while the other went red. Maybe one side of my charger doesn't work, and it never got charged. I'll report back when the light goes green.

I would actually be more concerned about the battery that stayed green when placed in the charger. Also, you said you were getting 5.8v, I don't think the meter is going to be that far off. The TI regulator is good about staying between 4.98 - 5.05 here. Something isn't right.

 

[gratefulme]

OK I tried it again with the now charged battery. Same thing. I guess There's nothing else I can do without being able to check these batteries in another device. No one lives near KC, MO That has one I can throw these in do they?

 

[smonomo]

The ground wire coming off the reg has a lot of insulation stripped, and looks suspiciously close to the red in wire/terminal.

 

[gratefulme]

That is a bad pic. I actually bent the pins so they on on a different level. Kinda hard to tell by a 2d pic. I can assure you there are no wires touching that shouldn't be. It may not be pretty, but believe it or not I've actually done a lot of soldering. Back in the old days of soldering jtags and what not for dishnetwork receivers. I've also modded every game system I've ever owned until the ps3. My wii was modded like two months after they came out lol. anyway I do no what not to do lol.

 

[doots]

Could be you have a bad battery. you could try taking out the TI and run straight to the atty connector to see if youre getting voltage that way. Could be your TI is bad?
Maybe bad battery allso.