Questions tagged [thermal]
Relating to temperature rise, the flow of heat, or cooling of components
4
votes
2answers
39 views
POWER MOSFET - Thermal Design
i have some doubts about with this thermal design?
first, the calculations and infos:
My load (a motor) uses an average current of 7A, I could not measure the current peak at the beginning of the ...
0
votes
1answer
37 views
Wire gauge and combined wires for 3D printer hotend through PCB
So I've been designing a wiring harness PCB for my 3D printer to provide connections and easily swappable tools. I settled on a TE 34-pin connector to use as input on the PCB. The current design ...
0
votes
1answer
53 views
LD1117V33 voltage regulator heatsink, thermal paste needed?
I want to screw a heatsink to my LD1117V33 voltage regulator. It's a normal 3mm screw and nothing inbetween. Do I need to use thermal paste or something like that?
It will be regulating 12V down to 3....
0
votes
1answer
56 views
Water-Based Heat Sink
I am trying to incorporate a TEC in a portable system. The heat from the interior of the system needs to be transfered to the exterior where it can be dissipated freely into the environment. Now, I ...
0
votes
1answer
38 views
Cold activated heater control
I would like to build a simple control circuit for a 12v silicone heating pad. I think what I'm looking to make is a thermally controlled relay: I want current to flow when the temperature is below ...
0
votes
1answer
25 views
Circuit thermal analysis in PSPICE and temperature coefficients
I am tying to perform a thermal analysis in pspice. Resistors needs two temperature coefficients as TC1 and TC2 (if we assume linear change of R vs. T, it's zero) in pspice. But in resistor datasheets ...
12
votes
2answers
248 views
What is reasoning behind the common wisdom of limiting the temperature rise of a PCB trace to 5/10/20°C?
When deciding on the trace thickness required to carry a certain amount of current on a PCB, the answer depends on how much temperature rise you are willing to accept. This leads the designer into the ...
0
votes
2answers
78 views
Understanding the thermal images of planar pcb coils
Why is only the first turn in the coil hotter compared to other two turns?
In this, only the turns of the top part seem to be hotter compared to the bottom.
Current through the coils is 2 A. It is ...
2
votes
1answer
53 views
General Peltier-tivity
[EDIT: Found a couple of 12715 units in the pile that did suck the full amperage, but despite excellent cooling of the hot side, could not deliver much cooling.]
I'm waist deep in project to keep ...
1
vote
1answer
33 views
Open-circuit alternator
Is it dangerous to run a permanent magnet alternator open-circuited? No current can flow so is all the power dissipated as heat? Is there even power generated in the inductive coils?
1
vote
0answers
33 views
Modeling the thermal part of the Time-current curve
G’ day,
I am working on designing protection devices for my research work and I am struggling to model the thermal part for the low voltage circuit breakers based on IEC standards.
Based on the ...
1
vote
1answer
56 views
Is there a difference between a tempco resistor and a thermistor?
That is, other than just the nomenclature.
2
votes
2answers
50 views
Temperature specificiations on MOSFET Safe Operating Area
Here's a SOA graph:
What I don't fully understand is the notes area at the bottom:
*Notes:
Tc=25°C
Tj=150°C
Single pulse
Every MOSFET datasheet seems to have a similar set of notes,...
0
votes
2answers
51 views
How do I determine the junction-to-ambient thermal resistance?
For a project I'm working on, I was considering using an AS7805 to supply low-noise 5V power to some sensors. (due to the uncertainty that resulted in asking this question, I've since changed to a ...
6
votes
2answers
791 views
LM317 - Calculate dissipation due to voltage drop
If I use a linear voltage regulator as LM317:
Input voltage = 24 V
Output voltage = 5 V (so a voltage drop of 19 V)
Mean load = 480 mA (peak load = 700 mA)
From the datasheet, I read that maximum ...
1
vote
2answers
36 views
Magnitude of \$I_{CBO}\$ in a typical transistor
I read in a book that \$I_{CBO}\$ doubles for every 10 degree rise in temperature and hence contributes to thermal runaway. However I am confused since essentially it is the reverse saturation current ...
15
votes
8answers
7k views
Why are electrically insulating heatsinks so rare? Is it just cost?
Edit: It seems my initial question (Why are there no insulating heatsinks?) was based on a false premise, and there are in fact insulating heatsinks--I just wasn't able to find them with a cursory ...
0
votes
2answers
61 views
Thermal calculation in case of duty cycle for a mosfet
For a multiplex LED matrix, I am intending to use two ULN2803's as sink source for 16 times 20 mA per column (channel).
However, maybe I will try a test with 100 mA LEDs (10% duty cycle). For that I ...
1
vote
1answer
29 views
Thermal generation of electron-hole couples and reverse biasing
I'm studying the PN junction and I have some problems figuring out thermal generation of couples electron-hole in reverse biasing.
The analysis is the standard one (for example, one can find it in the ...
1
vote
1answer
33 views
Macroscopic physical significance of Thermal Voltage in Diodes
Everywhere I search, the thermal voltage in diodes is described either as
the microscopic property related to the average energy of electrons due to thermal motion
The constant in the ideal diode ...
0
votes
1answer
50 views
How do I exactly calculate the amount of heat generated in MOSFET?
I am using two IRFP260N MOSFETs (datasheet) in parallel for my application. I am using it to drive a motor rated at 24VDC and consumes 8 to 10 Amps. I found some answers here and calculated the ...
1
vote
2answers
88 views
Why should the bias servo transistor not be placed on the main heat sink for a Sziklai pair?
The Wikipedia page on Sziklai pairs contains the following statement (emphasis mine)
Sziklai pairs can also have the benefit of superior thermal stability.
[...]. [Q]uiescent current is much more ...
0
votes
3answers
105 views
Cooling Methods for Voltage Regulators
I have a NCP1117 5V voltage regulator that is on an Arudino Mega. The Arduino Mega, with all of the necessary electronics parts for the project, draws around 200mA when operational. When using a ...
1
vote
3answers
260 views
heat dissipation in watts of equipment in a box
Here is the situation, some electrical equipment will be in low ambient temperatures and I need to make it warmer so that there is no damage to it.
I want to calculate how much power in watts is ...
1
vote
0answers
36 views
Thermal Faliure of thermal overload protected ICs
I have encountered a number of instances now where ICs that supposedly include "thermal overload protection" will still heat up until they fry. Examples: LM338,LM2576.
These devices datasheets ...
1
vote
1answer
55 views
Heating issues with solar charging circuit
I am using the above circuit to charge a 7.4V Li-ion Battery.With input MPPT voltage set at 12V, I have applied 13V input voltage to the circuit. The battery is charging at 1.4A. (according to the ...
1
vote
2answers
60 views
Does this circuit adequately represent the thermal considerations for a boost converter?
I'm new to electronics, and I'm trying to use a boost converter to get 5V at 1.2A from a lithium ion battery. I've selected the TPS61232 step up converter for this solution.
The datasheet has a ...
2
votes
2answers
102 views
install heatsink on BJT
I am facing the problem with the heat of transistor disturb sensor reading. Here the link refer problem
I am using BC548 transistor. It is a bit hot when operating because it disipates power around ...
2
votes
2answers
194 views
Shot or thermal noise of a MOS transistor
I'm trying to compare the shot and thermal noise contributions in a MOS transistor.
In the literature, the above-threshold MOS transistor has only thermal noise, which is found by integrating the ...
0
votes
1answer
110 views
Control board powered up with reverse polarity. power transistor blown. Is this repairable? [closed]
My dog chewed through the power cord. I 'repaired' it not paying attention to polarity. It was a 2A, 9V wall wart type power supply. The motherboard is from an elliptical exercise machine. The one ...
0
votes
2answers
106 views
Wha't the difference to use the junction to case thermal resistance instead of the junction to lead thermal resitance?
In case I have a diode, and I want to know it could dissipate the power, I have two values, but I can't choose between them:
- Junction to ambient thermal resitance \$R_{ja}\$
- Junction to lead ...
6
votes
3answers
745 views
How do electrons carry thermal energy in Peltier coolers?
I've read that when electrons enter from metal to semiconductor type N, they gain thermal energy and make that side cooler and the reverse happens when they leave semiconductor to the conductor.
Why ...
0
votes
2answers
48 views
Am I misunderstanding steady state power disspation calculations?
I am looking at the Littlefuse 5KP series. It says on the datasheet:
I am trying to understand how they arrive at \$P_D\$ = 8.0W.
Given thermal resistances of 40°C/W or 8.0°C/W, and 100°C ...
1
vote
2answers
201 views
Where would Iceo flow through and would it cause thermal runaway?
I was reading this page about thermal run away.
And it mentions:
Due to increase in the temperature of collector junction, Ico will
increase, Vbe will decrease.
But for Ico to increase Ic and ...
1
vote
4answers
109 views
MOSFET thermal resistance
I am trying to calculate the total thermal resistance of my FET to see what heat sinks are required, are the following calculations correct?
$$ Power = \frac{T_{jmax} - T_a}{\theta_{JC} + \theta_{CA}}...
1
vote
0answers
23 views
Low power thermal actuator/radiator head
There are a lot of thermal thermostats like this one that work on batteries.
I searched for an actuator that is working with ~5V but I only find 24V / 220V .
I can only find full systems that work ...
2
votes
1answer
107 views
Name of fabric insulator found inside motors
What is the name of the fabric sleeve insulator used for components (typically fuses) and solder joints found inside motor windings?
Can regular heat shrink tubing be used as a substitute?
Image by ...
1
vote
2answers
360 views
Can a thermal fuse of a higher rated current be used safely?
I want to replace a 115°C 250V 2A thermal fuse used in a fan motor. The only fuses available locally are 115°C 277V 15A. Can I use the higher current rated thermal fuse?
Since it is a thermal fuse, I ...
4
votes
1answer
193 views
IC product lifetime as function of junction temperature
If an IC is rated for an absolute maximum junction temperature of say 170 Celsius, obviously it is not recommended to operate there - but how drastically is product lifetime impacted if we are close, ...
0
votes
2answers
72 views
May I use a smaller wattage resistor as mosfet's gate driver for a very short time?
In a H-Bridge circuit, i am using gate resistors on all the mosfets.
My calculations for one of them, Gate voltage 4.5 V and Resistor 100 ohm gives me 45 mA, means 203 mW.
In a pulse of 16 us i ...
0
votes
1answer
39 views
Thermal hysteresis of shunt regulator
What is the meaning of the "Thermal hysteresis" in shunt regulator datasheet ?
Will it contribute to output tolerance ?
FYI: It's TL4050C50-Q1 datasheet.
18
votes
3answers
5k views
Why do 0 dB attenuators exist?
I am reading this paper : Upgrade of a low-temperature scanning tunneling microscope for electron-spin resonance and found that for thermalization, they use 0 dB attenuators.
Page 6: Having the ...
22
votes
8answers
6k views
How to solder a 70 °C (158 °F) thermal / temperature fuse
For my DMX project (schematics is not important), I soldered this temperature fuse which has just two leads (see picture below).
The fuse doesn't work (meaning it does not conduct electricity) ... ...
0
votes
4answers
139 views
BLDC Motor Performance at high altitude?
How does a BLDC motor performance change at high altitude where the air density is really low? For example, say I have a given BLDC motor with given torque-RPM performance curves. Now, I assume these ...
1
vote
2answers
60 views
Collisions of Thermal Impedances
As shown in the picture below, thermal impedances of an IGBT device depends on the temperature. However, there is a strange phenomenon as follows. While with increasing the temperature, steady-state ...
1
vote
1answer
45 views
Do thermal cutoffs exist that would work with a line that is 40-75V 0.5A and a max temp of ~85°C?
I have a bunch of COB LEDs that I am going to wire in series using an LED driver. The driver gives off between 40-75V and 0.5A max. The circuit should run around 70V and 0.5A.
Due to space ...
-7
votes
1answer
114 views
Light source that withstands extreme conditions [closed]
I am designing an aircraft obstruction light, and Federal Aviation Administration (FAA) requires crazy requirements for their standards. One standard goes as following (From FAA AC 150/5345-43H):
4....
0
votes
3answers
193 views
thermal fuse as electrical fuse
I am trying to understand the spec of a Datasheet of a thermal fuse.
for example the one below :
https://nl.farnell.com/panasonic-electronic-components/eyp2bn134/fuse-thermal-cut-off-2a/dp/1832031
...
0
votes
1answer
250 views
Waterproofing MLX90640 far infrared thermal sensor
I would like to use the MLX90640 far infrared thermal sensor array on a car as a "night vision" camera. Since glass blocks thermal radiation I have to install it outside the cabin. Is it possible to ...
3
votes
1answer
307 views
PCB power supply layout considerations
I'm designing a circuit that steps down 230v AC to 12v DC and then uses an MCP73213 IC to charge a 7.4v li-po battery. There is also functionality to switch over to the battery supply if there is no ...
