Making Game: Computer reboots/freezes when using a lot of (graphics) resources

Original Source Link

Whenever I would render (Cycles) using my GPUs (2x GTX 970) eventually my computer would freeze (if music was playing it would give a loud distortion pop when it happened). Then I updated my BIOS to the latest version and it stopped doing that but now it reboots when I play certain resource heavy games (Terminator Resistance in this case, for some reason Doom Eternal is not a problem).

Normally I’d think that these reboots would be a PSU issue but it’s really beefy (850W and bought in the last year). My motherboard is pretty old (bought in 2012). Could that be the issue? Another option is that the main GPU (one of the GTX 970s) is no good. They’re both second hand.

Another issue I had recently was that after replacing the BIOS battery the computer wouldn’t boot with anything in the PCI-e slots. After upgrading the BIOS I was able to boot just fine with both GPUs.

Here’s some info from CPU-Z:

Processors Information
-------------------------------------------------------------------------

Socket 1            ID = 0
    Number of cores     4 (max 4)
    Number of threads   4 (max 4)
    Name            Intel Core i5 3570K
    Codename        Ivy Bridge
    Specification       Intel(R) Core(TM) i5-3570K CPU @ 3.40GHz
    Package (platform ID)   Socket 1155 LGA (0x1)
    CPUID           6.A.9
    Extended CPUID      6.3A
    Core Stepping       E1/L1
    Technology      22 nm
    TDP Limit       77.0 Watts
    Tjmax           105.0 °C
    Core Speed      3703.1 MHz
    Multiplier x Bus Speed  37.0 x 100.1 MHz
    Base frequency (cores)  100.1 MHz
    Base frequency (ext.)   100.1 MHz
    Stock frequency     3400 MHz
    Instructions sets   MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, EM64T, VT-x, AES, AVX
    Microcode Revision  0x21
    L1 Data cache       4 x 32 KBytes, 8-way set associative, 64-byte line size
    L1 Instruction cache    4 x 32 KBytes, 8-way set associative, 64-byte line size
    L2 cache        4 x 256 KBytes, 8-way set associative, 64-byte line size
    L3 cache        6 MBytes, 12-way set associative, 64-byte line size
    Max CPUID level     0000000Dh
    Max CPUID ext. level    80000008h
    Cache descriptor    Level 1, D, 32 KB, 2 thread(s)
    Cache descriptor    Level 1, I, 32 KB, 2 thread(s)
    Cache descriptor    Level 2, U, 256 KB, 2 thread(s)
    Cache descriptor    Level 3, U, 6 MB, 16 thread(s)
    FID/VID Control     yes


    IBRS            supported, disabled
    IBPB            supported
    STIBP           supported, disabled
    RDCL_NO         no
    IBRS_ALL        not supported
    Turbo Mode      supported, enabled
    Max non-turbo ratio 34x
    Max turbo ratio     38x
    Max efficiency ratio    16x
    Min Power       60 Watts
    O/C bins        unlimited
    Ratio 1 core        38x
    Ratio 2 cores       38x
    Ratio 3 cores       37x
    Ratio 4 cores       36x
    TDP Level       77.0 W @ 34x

    Temperature 0       58 degC (136 degF) (Package)
    Temperature 1       54 degC (129 degF) (Core #0)
    Temperature 2       56 degC (132 degF) (Core #1)
    Temperature 3       57 degC (134 degF) (Core #2)
    Temperature 4       60 degC (140 degF) (Core #3)
    Voltage 0       1.07 Volts (VID)
    Power 00        23.11 W (Package)
    Power 01        16.85 W (IA Cores)
    Power 02        n.a. (GT)
    Power 03        6.26 W (Uncore)
    Clock Speed 0       3703.11 MHz (Core #0)
    Clock Speed 1       3703.11 MHz (Core #1)
    Clock Speed 2       3703.11 MHz (Core #2)
    Clock Speed 3       3603.03 MHz (Core #3)
    Core 0 max ratio    38.0 (effective 38.0)
    Core 1 max ratio    38.0 (effective 38.0)
    Core 2 max ratio    38.0 (effective 38.0)
    Core 3 max ratio    38.0 (effective 38.0)Processors Information
-------------------------------------------------------------------------

Socket 1            ID = 0
    Number of cores     4 (max 4)
    Number of threads   4 (max 4)
    Name            Intel Core i5 3570K
    Codename        Ivy Bridge
    Specification       Intel(R) Core(TM) i5-3570K CPU @ 3.40GHz
    Package (platform ID)   Socket 1155 LGA (0x1)
    CPUID           6.A.9
    Extended CPUID      6.3A
    Core Stepping       E1/L1
    Technology      22 nm
    TDP Limit       77.0 Watts
    Tjmax           105.0 °C
    Core Speed      3703.1 MHz
    Multiplier x Bus Speed  37.0 x 100.1 MHz
    Base frequency (cores)  100.1 MHz
    Base frequency (ext.)   100.1 MHz
    Stock frequency     3400 MHz
    Instructions sets   MMX, SSE, SSE2, SSE3, SSSE3, SSE4.1, SSE4.2, EM64T, VT-x, AES, AVX
    Microcode Revision  0x21
    L1 Data cache       4 x 32 KBytes, 8-way set associative, 64-byte line size
    L1 Instruction cache    4 x 32 KBytes, 8-way set associative, 64-byte line size
    L2 cache        4 x 256 KBytes, 8-way set associative, 64-byte line size
    L3 cache        6 MBytes, 12-way set associative, 64-byte line size
    Max CPUID level     0000000Dh
    Max CPUID ext. level    80000008h
    Cache descriptor    Level 1, D, 32 KB, 2 thread(s)
    Cache descriptor    Level 1, I, 32 KB, 2 thread(s)
    Cache descriptor    Level 2, U, 256 KB, 2 thread(s)
    Cache descriptor    Level 3, U, 6 MB, 16 thread(s)
    FID/VID Control     yes


    IBRS            supported, disabled
    IBPB            supported
    STIBP           supported, disabled
    RDCL_NO         no
    IBRS_ALL        not supported
    Turbo Mode      supported, enabled
    Max non-turbo ratio 34x
    Max turbo ratio     38x
    Max efficiency ratio    16x
    Min Power       60 Watts
    O/C bins        unlimited
    Ratio 1 core        38x
    Ratio 2 cores       38x
    Ratio 3 cores       37x
    Ratio 4 cores       36x
    TDP Level       77.0 W @ 34x

    Temperature 0       58 degC (136 degF) (Package)
    Temperature 1       54 degC (129 degF) (Core #0)
    Temperature 2       56 degC (132 degF) (Core #1)
    Temperature 3       57 degC (134 degF) (Core #2)
    Temperature 4       60 degC (140 degF) (Core #3)
    Voltage 0       1.07 Volts (VID)
    Power 00        23.11 W (Package)
    Power 01        16.85 W (IA Cores)
    Power 02        n.a. (GT)
    Power 03        6.26 W (Uncore)
    Clock Speed 0       3703.11 MHz (Core #0)
    Clock Speed 1       3703.11 MHz (Core #1)
    Clock Speed 2       3703.11 MHz (Core #2)
    Clock Speed 3       3603.03 MHz (Core #3)
    Core 0 max ratio    38.0 (effective 38.0)
    Core 1 max ratio    38.0 (effective 38.0)
    Core 2 max ratio    38.0 (effective 38.0)
    Core 3 max ratio    38.0 (effective 38.0)

Chipset
-------------------------------------------------------------------------

Northbridge         Intel Ivy Bridge rev. 09
Southbridge         Intel Z77 rev. 04
Graphic Interface       PCI-Express
PCI-E Link Width        x16
PCI-E Max Link Width        x16
Memory Type         DDR3
Memory Size         8 GBytes
Channels            Single
Memory Frequency        800.7 MHz (1:6)
CAS# latency (CL)       11.0
RAS# to CAS# delay (tRCD)   11
RAS# Precharge (tRP)        11
Cycle Time (tRAS)       30
Command Rate (CR)       1T
Host Bridge         0x0150

Mainboard Model     Z77M-D3H (0x00000201 - 0x00B6E5F6)

Display Adapters
-------------------------------------------------------------------------

Display adapter 0   
    ID          0x1080204
    Name            NVIDIA GeForce GTX 970
    Board Manufacturer  Micro-Star International Co., Ltd. (MSI)
    Revision        A1
    Codename        GM204
    Technology      28 nm
    Memory size     4 GB
    Memory type     GDDR5
    PCI device      bus 1 (0x1), device 0 (0x0), function 0 (0x0)
    Vendor ID       0x10DE (0x1462)
    Model ID        0x13C2 (0x3160)
    Revision ID     0xA1
    Performance Level   0
        Core clock  135.0 MHz
        Memory clock    324.0 MHz

Display adapter 1   
    ID          0x1080204
    Name            NVIDIA GeForce GTX 970
    Board Manufacturer  Micro-Star International Co., Ltd. (MSI)
    Revision        A1
    Codename        GM204
    Technology      28 nm
    Memory size     4 GB
    Memory type     GDDR5
    PCI device      bus 2 (0x2), device 0 (0x0), function 0 (0x0)
    Vendor ID       0x10DE (0x1462)
    Model ID        0x13C2 (0x3160)
    Revision ID     0xA1
    Performance Level   0
        Core clock  135.0 MHz
        Memory clock    324.0 MHz

Win32_VideoController       AdapterRAM = 0xFFF00000 (4293918720)
Win32_VideoController       AdapterRAM = 0xFFF00000 (4293918720)
Win32_VideoController       DriverVersion = 26.21.14.4587
Win32_VideoController       DriverVersion = 26.21.14.4587
Win32_VideoController       DriverDate = 04/03/2020
Win32_VideoController       DriverDate = 04/03/2020

Tagged : / / / /

Server Bug Fix: Tantalum Capacitor Explodes When Engine Starts

Original Source Link

I designed a circuit using a SMPS voltage regulator based on the tps65261rhbr triple synchronous buck converter. The circuit is rated for up to 18V. It is connected to a 12V lawnmower battery, which also starts and powers a gasoline engine that returns charge to the battery with an alternator.

The circuit has worked perfectly over many hours of testing and switching power on and off before I connected and started the engine. Immediately upon starting the engine it failed: one of the 25V 47uF tantalum capacitors (TPSD476K025R0150) feeding the SMPS exploded.

My oscilloscope has a max of 10V, so I can’t see what the input voltage waveform looks like when the engine starts and runs. I tried anyway, and I see that when the engine is started the voltage briefly dips under 10V, but outside of that brief blip it is clipped to 10V so I can’t tell what’s happening. I assume the voltage must have exceeded 25V for the capacitor to explode.

I’m considering switching to higher voltage (50V?) aluminum polymer bulk capacitors and a high input voltage rated 12V LDO before the SMPS to protect against input voltage spikes.

Does this seem like a good approach? Should I get a better scope or build a voltage divider to see what’s really happening? Does anyone have any experience with powering circuits from an engine alternator and battery in parallel that can weigh in on this power supply design?

Tantalums are very sensitive to overvoltage so you have to derate them if you want to use them. They are already typically derated by 30-50% in normal use but you are connect them up directly to a gas engine. Gasoline engines are a very harsh source of power so you should be installing transient suppression and the like anyways such as TVS diodes or MOVs to suppress voltage spikes. Regardless, you probably shouldn’t have chosen tantalums in the first place as the input decoupling capacitors knowing they would be directly exposed to something so harsh as a generator.

No LDO, or any type of linear regulator that matter. Having a linear regulator defeats the purpose of having an the efficiency of an SMPS and they are too delicate for the protection task anyways. Furthermore, 18V to 12V with a linear regulator is too much heat for any remotely moderate levels of current.

Get a big TVS diode with a working voltage (not a breakdown voltage) as close to but greater than the battery voltage at full charge. It would help if you could scope to see what the startup transients, and the transients in general are like. There’s a chance the TVS diode won’t be able to handle the power in which case you need to go with a metal oxide varistor (MOV). But if a TVS diode can do it, then a TVS diode will be better. MOVs do not not clamp as well as TVS diodes and have an inherent wear out mechanism each time they conduct so you don’t want to accidentally undersize it if you expect it to be constantly experiencing strikes or else it will wear out early, but they can be made a lot bigger (like bricks!) so can found in much higher power levels.

And go ahead and toss in that 50V aluminum polymer. You probably don’t need quite so high as 50V though. Aluminum polymers don’t need very much derating.

Might as well toss in a fuse while you’re at it.

Tantalum capacitors have a very low effective internal series resistance. A quick, low impedance fed change in voltage from the alternator can cause the current through the tantalum capacitor to exceed its maximum allowed value and blow up the capacitor.
I’ve experienced this behaviour once in a 40 kW IGBT inverter, (repeatedly) blowing out the IGBTs, and the remedy was to insert small series resistances in series in order to limit the equalisation currents to acceptable values.
Could it be that you are using an old fashioned alternator with carbon brushes and commutator?

Tagged : / /

Linux HowTo: Why would an IBM netvista suddenly fail to turn on?

Original Source Link

I have an old Pentium IBM Netvista desktop PC with I believe an ATX power supply. For reference, the cable going into the motherboard from the power is 10 pins long by 2 wide and the info on the power supply is:

IBM part #: 24P6880
IBM FRU # 24P6883

The last time I used the PC was about 3 months ago. Back then when I turned the power on from the house power supply (monitor power was also connected to the house supply) the fans started going for 3 seconds then shut off then I press the power button once and everything turns on normally.

Now (3 months later) I do the same thing again (exactly same setup as before), except this time when I turn the power on from the same house supply (same voltage and all), the monitor turns on, but the desktop does not. I may have been lucky one time when I turned the power off and on a few random seconds later but when I did manage to turn it on, I got a few random beeps and the system gave an error. I was able to run setup at that point and save settings, but after exiting setup, the screen goes blank. So I turned the power off, then shortly after, I tried turning it on again 10 times in a row with about 30 seconds break in-between and nothing in the desktop wanted to turn on. No fan, nothing. I then begin to unplug all the peripherals except motherboard and tried again, and still nothing.

Could this all be a power supply thing?

Only thing I didn’t try which is taped up when I got it was the voltage selector switch on the back of the supply. Do you think that would help? what should I do?

I then decided to take the power supply out of the PC to see whats wrong with it, and when I did a continuity test on a power connector, it turned out everything was short-circuited (aka 12V, 5V and ground were electrically all connected together).

So now I’m gonna replace the supply and pray for the best.

Tagged : / / / /

Making Game: Why would an IBM netvista suddenly fail to turn on?

Original Source Link

I have an old Pentium IBM Netvista desktop PC with I believe an ATX power supply. For reference, the cable going into the motherboard from the power is 10 pins long by 2 wide and the info on the power supply is:

IBM part #: 24P6880
IBM FRU # 24P6883

The last time I used the PC was about 3 months ago. Back then when I turned the power on from the house power supply (monitor power was also connected to the house supply) the fans started going for 3 seconds then shut off then I press the power button once and everything turns on normally.

Now (3 months later) I do the same thing again (exactly same setup as before), except this time when I turn the power on from the same house supply (same voltage and all), the monitor turns on, but the desktop does not. I may have been lucky one time when I turned the power off and on a few random seconds later but when I did manage to turn it on, I got a few random beeps and the system gave an error. I was able to run setup at that point and save settings, but after exiting setup, the screen goes blank. So I turned the power off, then shortly after, I tried turning it on again 10 times in a row with about 30 seconds break in-between and nothing in the desktop wanted to turn on. No fan, nothing. I then begin to unplug all the peripherals except motherboard and tried again, and still nothing.

Could this all be a power supply thing?

Only thing I didn’t try which is taped up when I got it was the voltage selector switch on the back of the supply. Do you think that would help? what should I do?

I then decided to take the power supply out of the PC to see whats wrong with it, and when I did a continuity test on a power connector, it turned out everything was short-circuited (aka 12V, 5V and ground were electrically all connected together).

So now I’m gonna replace the supply and pray for the best.

Tagged : / / / /

Linux HowTo: New Power Supply doesn’t work with a specific motherboard

Original Source Link

I just bought a new power supply Corsair CX430 V2 in order to meet the needs of a new graphics card I hope to install. The motherboard is the micro-ATX form factor Asus P5KPL-AM/PS running a Intel C2D E7200 CPU and 2x2GB of DDR2-800 RAM.

Problem: the computer doesn’t boot with the new PSU.

The case Power LED turns on alongwith the PSU and CPU fan for about 3-4 seconds before switching off. The comp. works just fine with the current PSU which is a local brand 400W conforming to ATX12V1.3. The new PSU works fine with three other motherboards: two AMD-based ones and one old Gigabyte LGA775 board running a P4 HT chip.

On my motherboard, the following combinations were tried with no success:
1)20+4 pin connector plugged in; each half of the 4+4 ATX 12V connector plugged in, by turn.
2)20 pin connector plugged in; each half of the 4+4 ATX 12V connector plugged in, by turn.
3)20+4 pin connector plugged in; the 4+4 ATX 12V connector not plugged in.

In the above attempts, no other peripherals or add-on cards were present.

With the old PSU, the 20+4 as well as the CPU 4-pin connector is plugged in.

My dealer-engineer is blaming it on motherboard compatibility but that doesn’t seem to be the issue.

The motherboard manual on p1-28 says, “we recommend that you use a power supply unit (PSU) that complies with ATX 12 V Specification 2.0 (or later version) and provides a minimum power of 400 W.“. The new PSU, as per the manufacturer, “is backward compatible with ATX12V 2.2 and ATX12V 2.01 systems“.

Any suggestions on what the issue may be or how to proceed next?

The biggest problem is different manufactures produce power supplies with different amounts of amps on each voltage. The main ones are 3v,5v, and 12v. On a 400w or 430w PSU if you 5v has 50A then the 12V is going to have a low number of amps.

We don’t know what your “New video card” is, but chances are a higher watt power supply would make your problems go away. The specs say your new PSU only has 28A on the 12v supply.

The 400w psu may have more amps on the 12v channel and less on the 5v and therefore it worked.

However to avoid all this non-sense get a 550w or 600w psu and you will have enough amps on all voltages.

I am not sure if this applies in your situation, but, in my case, the reason the Corsair PSU would not remain powered on turned out to be that the load placed on the PSU was “not large enough”.

Corsair apparently designs their PSUs this way as (I’m guessing) a fail safe?

Or at least they did. Since your question (and mine) are now over 7 years old, I have no idea how a current Corsair PSU would work. But this certainly appears to be how it works for my now elderly Corsair CX430 430w PSUs.

Tagged : / / / /

Making Game: New Power Supply doesn’t work with a specific motherboard

Original Source Link

I just bought a new power supply Corsair CX430 V2 in order to meet the needs of a new graphics card I hope to install. The motherboard is the micro-ATX form factor Asus P5KPL-AM/PS running a Intel C2D E7200 CPU and 2x2GB of DDR2-800 RAM.

Problem: the computer doesn’t boot with the new PSU.

The case Power LED turns on alongwith the PSU and CPU fan for about 3-4 seconds before switching off. The comp. works just fine with the current PSU which is a local brand 400W conforming to ATX12V1.3. The new PSU works fine with three other motherboards: two AMD-based ones and one old Gigabyte LGA775 board running a P4 HT chip.

On my motherboard, the following combinations were tried with no success:
1)20+4 pin connector plugged in; each half of the 4+4 ATX 12V connector plugged in, by turn.
2)20 pin connector plugged in; each half of the 4+4 ATX 12V connector plugged in, by turn.
3)20+4 pin connector plugged in; the 4+4 ATX 12V connector not plugged in.

In the above attempts, no other peripherals or add-on cards were present.

With the old PSU, the 20+4 as well as the CPU 4-pin connector is plugged in.

My dealer-engineer is blaming it on motherboard compatibility but that doesn’t seem to be the issue.

The motherboard manual on p1-28 says, “we recommend that you use a power supply unit (PSU) that complies with ATX 12 V Specification 2.0 (or later version) and provides a minimum power of 400 W.“. The new PSU, as per the manufacturer, “is backward compatible with ATX12V 2.2 and ATX12V 2.01 systems“.

Any suggestions on what the issue may be or how to proceed next?

The biggest problem is different manufactures produce power supplies with different amounts of amps on each voltage. The main ones are 3v,5v, and 12v. On a 400w or 430w PSU if you 5v has 50A then the 12V is going to have a low number of amps.

We don’t know what your “New video card” is, but chances are a higher watt power supply would make your problems go away. The specs say your new PSU only has 28A on the 12v supply.

The 400w psu may have more amps on the 12v channel and less on the 5v and therefore it worked.

However to avoid all this non-sense get a 550w or 600w psu and you will have enough amps on all voltages.

I am not sure if this applies in your situation, but, in my case, the reason the Corsair PSU would not remain powered on turned out to be that the load placed on the PSU was “not large enough”.

Corsair apparently designs their PSUs this way as (I’m guessing) a fail safe?

Or at least they did. Since your question (and mine) are now over 7 years old, I have no idea how a current Corsair PSU would work. But this certainly appears to be how it works for my now elderly Corsair CX430 430w PSUs.

Tagged : / / / /

Making Game: Double boot after AC power reset?

Original Source Link

My computer has been doing this for so long I basically accepted it as normal: any time AC power is lost, intentionally or not, the PC takes 2 tries to boot. Never 3, always 2. So if I toggle the PSU or unplug and move the PC, double boot inc.

When it happens, the first try is only a couple of seconds, clicks off, back on, then goes through normal boot instead of fast boot. The Power Plan often defaults back to High Performance too, but I dont know if its related.

Certain BIOS changes (but not all) will cause it as well, when it restarts to apply them.

I finally decided to ask about it because I’ve never found anything, but today it booted on the first try after moving it. For the first time in at least a year, more like two. I removed a couple older HDDs for the moment, and apparently that did it?

The only hint I’ve found online is RAM timings, but I’ve tried all kinds of settings in the course of overclocking, and diagnosing other issues. The double boot has always been consistent until today. I dont miss it… I just wanna understand man…

Tagged : / / / /

Linux HowTo: Is an Abtec CE2 hb1003 (550W) enough to power an GTX 970? [duplicate]

Original Source Link

Would an Abtec CE2 hb1003 (http://www.acbel.com/eng/Product.aspx?id=42&&sd=31&&pid=242) be enough to power a GTX 970 or 960 4gb? Thanks

Per these specs (http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-960/specifications) the 500W CE2 HB1003 power supply appears to be sufficient for the Geforce GTX 960 (only requires 400W, ~80%), but I would not use it to power the 970 since it needs 500W. This power supply has an OPP (over power protection) of 550W meaning it will protect itself by disconnecting or dropping power output when requirements get to 550W – that seems critically close to a problem, IMO.

This is my suggestion based on 25+ years of electrical experience.

Tagged : / /

Making Game: Is an Abtec CE2 hb1003 (550W) enough to power an GTX 970? [duplicate]

Original Source Link

Would an Abtec CE2 hb1003 (http://www.acbel.com/eng/Product.aspx?id=42&&sd=31&&pid=242) be enough to power a GTX 970 or 960 4gb? Thanks

Per these specs (http://www.geforce.com/hardware/desktop-gpus/geforce-gtx-960/specifications) the 500W CE2 HB1003 power supply appears to be sufficient for the Geforce GTX 960 (only requires 400W, ~80%), but I would not use it to power the 970 since it needs 500W. This power supply has an OPP (over power protection) of 550W meaning it will protect itself by disconnecting or dropping power output when requirements get to 550W – that seems critically close to a problem, IMO.

This is my suggestion based on 25+ years of electrical experience.

Tagged : / /

Server Bug Fix: Obtaining 4-4.2V rail from 5V output of LM7805 voltage regulator

Original Source Link

I’m creating a numitron clock with 4xIV-9 tubes (seven-segment filament displays) and have decided to illuminate them using shift registers controlled by an arduino. Each segment takes a voltage of 4-4.2V and around 17-20mA of current.

My voltage I have available is a 5V output voltage from an LM7805 voltage regulator IC. I need to power 4 high current shift registers (TPIC6B595), each with an expected maximum output current of 200mA. Owing to this, the 4-4.2V rail needs to be able to handle a maximum current draw of around 800mA.
I was considering using a simple potential divider however calculated that the required power losses greatly exceed that of the standard resistors that I have available.
I was also considering using a diode to drop the voltage however the forward voltage is a function of the current; therefore as the current can vary from the extremes of 0mA to 800mA I did not think a diode would be appropriate.

Any suggestions on how to obtain 4-4.2ish V rail would be much appreciated.
Many thanks.

Replace the 7805 with a 1Amp or more adjustable regulator and set it to 4.2 volts. Run both the arduino and everything from that instead of running it off the 5V. The Arduino will be fine with 4.2 volts without any issue, and it makes it easier since you dont have to worry about level translation for the input lines either.

The Atmega microcontroller in the Arduino will run fine at 4V, so the simplest solution would be to power the whole thing from a 4-4.2V switching power supply instead of using a voltage regulator.

Since 4.2V is the end of charge voltage of LiIon cells, there are plenty of off the shelf 4.2V power supplies available.

Failing that, you can use a SMPS or wall wart with adjustable voltage, or simply change the feedback resistor in a 5V 1-2 Amps USB “phone charger” to make it output 4.2V instead of 5V.

I am assuming that the input voltage that feeds the 7805 regulator is significantly higher than 5V. If so, I would use a small adjustable SMPS Buck Regulator that operates from that input supply.

You can either build one yourself or simply purchase one of the very inexpensive boards / modules from your favourite supplier.

Set the output voltage to the desired value.

The advantage of this approach is that you are not dissipating all that power in the 7805 regulator.

Use an adjustable voltage regulator.

Use a low-dropout adjustable voltage regulator. Measure the output voltage of the 7805 and make sure you are really getting at least 5V, then look for a regulator that will work with an input-output voltage difference of, say, 0.5V or less.

Tagged : / / /