I am losing 0.5 volts

Thread Starter

igeorge

Joined Jul 2, 2010
58
Hello,
I need help as on the attached pdf drawing or eagle schematic, i am getting 4.5 volts at ESP and RFID reader.
How it works:
At the input it is 12 VDC, going through 5v dc regulator.
The 5 vdc goes to Lipo charger and also to T1.
T1 it is a switch between 12vdc in and battery.
Then, power goes to an Adafruit minibooster.
The 5 vdc from booster goes through a Start/Stop circuit.
I use it to save battery power.
When you press the Push button, 5 volts goes to ESP , 5 volts power pin.
When ESP32 get power, put Control line High, and this one latch the ON state.
After i finished the work with ESP, i just turn LOW the control line and power it is shut down from battery/or 12vdc.
The 5 volts goes to the RDM6300 power pin.
Even though it is just a small current on RDM or ESP, the voltage after switch is just 4.5 volts and the card reader cannot work.
Can anybody tell me what i am doing wrong ?
Thank you
 

Attachments

Dodgydave

Joined Jun 22, 2012
10,085
Have you built this on a pcb or is it
a software programme?

I would be measuring between the 5V supply to the card reader positive to see what voltage is dropping, and also on the ground sides.
 
Last edited:

Thread Starter

igeorge

Joined Jul 2, 2010
58
Sorry for late reply. I just got your email now. My mail server was down.
The circuit is buited on anormal pcb.
The voltage on RFID power and ground is 4.5 v.
The same voltage is on ESP32 at 5Vots In pin.
The voltage after Murrata regulator is 5 volts.
 

dcbingaman

Joined Jun 30, 2021
495
Take a look at the voltage drop across D1. According to the device datasheet this can be as high as 0.5V. According to the following taken from D1 datasheet at ambient temperature even at only 10mA drop is still over 0.2V

Capture3.PNG
 

Thread Starter

igeorge

Joined Jul 2, 2010
58
Thank you for suggestion dcbingaman.
But if you look close, the diode is before Adafruit buster, which mean the booster will get 4.5 volts at input and have 5 volts at output.
I worry mostly about IRF7317 which get 3.3 volts on the gate of N mosfet.
For me the mosfets are a tale from "Touthand and one nights" Only Sherezada knows the meaning...
 

dcbingaman

Joined Jun 30, 2021
495
Thank you for suggestion dcbingaman.
But if you look close, the diode is before Adafruit buster, which mean the booster will get 4.5 volts at input and have 5 volts at output.
I worry mostly about IRF7317 which get 3.3 volts on the gate of N mosfet.
For me the mosfets are a tale from "Touthand and one nights" Only Sherezada knows the meaning...
Sorry missed that little detail. Yea, I looked at that chip now. Sure enough can boost up the whole way down less than 3.5V. I am confused now because the TPS61023 is a 6 pin device that requires an external inductor and other things for proper use, am I missing something? I take it that is some sort of plug in module that simply has a TPS61023 on it?
 

dcbingaman

Joined Jun 30, 2021
495
Thank you for suggestion dcbingaman.
But if you look close, the diode is before Adafruit buster, which mean the booster will get 4.5 volts at input and have 5 volts at output.
I worry mostly about IRF7317 which get 3.3 volts on the gate of N mosfet.
For me the mosfets are a tale from "Touthand and one nights" Only Sherezada knows the meaning...
I am not observing any issues with the IRF7317 according to the datasheet that dude can carry well over 10Amps with Vgs=3.3V while the PFET is getting a solid -5V, again datasheet indicates that is plenty to turn it on and saturate it.
 

dcbingaman

Joined Jun 30, 2021
495
Thank you for suggestion dcbingaman.
But if you look close, the diode is before Adafruit buster, which mean the booster will get 4.5 volts at input and have 5 volts at output.
I worry mostly about IRF7317 which get 3.3 volts on the gate of N mosfet.
For me the mosfets are a tale from "Touthand and one nights" Only Sherezada knows the meaning...
Are we sure the booster is not going into pass through mode? The voltages are very close to one another. Consider the fact that when the circuit turns on D1 has no current and 5V will be seen by the booster even if just for a short time. Being that it is enabled by the same voltage it will be turning on at the same time while 5V is still on the input due to no current through D1. Naturally this is a short time, but the booster might be 'latching' into pass through mode because of this.
 

Thread Starter

igeorge

Joined Jul 2, 2010
58
To be honest, i do not know very well how it works.
The first portion until the Booster i copied from Adafruit on ESP32 module which has also a battery charger.
Then i put the booster module, and just after it I put the Start/Stop circuit - IRF7317.
From the P-fet i expected to get 5 volts, which i do not get it.
 

Irving

Joined Jan 30, 2016
2,308
Just to be clear, you're saying you only get 4.5v on the 5vRUN line after the button is pressed - it never goes to 5v? What is output voltage of booster at source of P-channel FET?

A simulation of the IRF7317 suggests no issue there, so my guess is you're not getting 5V out of the booster on load.

1625141319479.png
 
Last edited:

Thread Starter

igeorge

Joined Jul 2, 2010
58
Hello Irving,
Thank you a lot for your simulation.
After all the suggestions and investigations, I have a feeling that something might be wrong with the PCB (China made).
I did not inspect it before mounting the components.
My next steps, long road but sure:
Build a board up to IRF7317, and put a jumper wire to bypass IRF7317 and connect directly output of the booster to ESP and RFID board, then measure the voltage.
If it is still 4.5, then booster is a problem, but if it is 5 volts, then investigate further IRF7317.
Also, i will look at the microscope at the PCB before installing the parts. The traces are 10 thou for regular data and 15 thou for
power. The spacing also is big , 10 thou or more. Will be easier to look.
I tried to simulate on proteus 8 but it was not so precise like Pspice.
To rebuild the board and do tests probably will take a day.
I will update you ASAP.
Attached is a new proposed schematic for test.
 

Attachments

Irving

Joined Jan 30, 2016
2,308
Rather than build a new board, why not just measure the voltage at 5V_IN before and after pressing the button. If its <5v before then the booster is faulty or needs adjusting. If 5V_IN is 5V before pressing the button but drops to 4.5v after then either the booster is faulty or you are drawing too much current from it.
If its 5v but the 5V_RUN output from the 7137 is still 4.5V then the 7137 is faulty or you're drawing a lot of current...

15thou (15mil) is good for 1.2A and 0.02v per cm drop.
 

Thread Starter

igeorge

Joined Jul 2, 2010
58
Unfortunately i was in rush and removed the Booster as was so hot.
In top of that, i also removed the IRF.
Bottom line, i prefer make a new than patch.
Sorry.
 

Irving

Joined Jan 30, 2016
2,308
Unfortunately i was in rush and removed the Booster as was so hot.
In top of that, i also removed the IRF.
Bottom line, i prefer make a new than patch.
Sorry.
If the booster was anything more than gently warm that suggests it was either faulty or overloaded!
 

Thread Starter

igeorge

Joined Jul 2, 2010
58
Good news
I made a new board and full loaded, it keeps the 5 volts.
No drop to 4.5.
I used the same ESP32 and the same RFID reader. I changed the Booster only.
I will do longer run and see if the booster start heating again and voltage drop.
If no news from me it means "No news good news".
If something goes wrong i will comeback.
Thank you very much to all of you for help and support.
 
Top