53
votes
Accepted
What does a "fork" symbol mean on a schematic?
Chassis ground. See:
simulate this circuit – Schematic created using CircuitLab
(Illustration from Ground - Ultimate Electronics Book)
- 3,694
41
votes
What does a "fork" symbol mean on a schematic?
Normally it would mean chassis ground.
But it would probably mean the substrate in the case of an IC schematic.
The substrate is usually connected to the ground pin or the most negative voltage (...
- 34.2k
33
votes
Why do we use capacitors in parallel with DC motors?
Generally a 0.01~0.1uF capacitor is wired across brushed DC motors to reduce radio frequency EMI caused by arcing between the brushes and commutator. Sometimes two capacitors are wired in series, with ...
- 57k
27
votes
What does a "fork" symbol mean on a schematic?
This from IEEE Std 315 for that symbol:
"A conducting connection to a chassis or frame, or equivalent chassis connection of a printed-wiring board. The chassis or frame (or equivalent chassis ...
- 11.1k
25
votes
Why do motor drives have multiple bus capacitors of small value capacitance instead of a single bus capacitor of large value?
Sure having enough capacitance is one parameter. But capacitors have series resistance which limits how much peak current can be drawn from a capacitor. Capacitors also have series inductance which ...
- 172k
17
votes
Why do motor drives have multiple bus capacitors of small value capacitance instead of a single bus capacitor of large value?
Other answers have already mentioned the main factors which determine that choice: lower total ESR, lower total inductance, better heat handling capability, etc.
I'll add one more aspect that has ...
17
votes
Why do motor drives have multiple bus capacitors of small value capacitance instead of a single bus capacitor of large value?
Higher ripple current capability, lower ESR and sometimes better form factor (eg. shorter) to fit in a convenient spot in the enclosure are likely reasons.
More surface area of the capacitor means ...
14
votes
Why do we use capacitors in parallel with DC motors?
DC motors use brushes on the commutators. These spark due to inductance of the coils as they switch from segment to segment.
Figure 1. Communtators and brushes. Image source: eReplacmentParts.
The ...
- 181k
10
votes
Accepted
Why does my MIC4605 keep blowing up?
On your layout the decoupling cap (finger-painted red) is very far away from the chip, there is a 5R resistor in series (purple) and the current loop area (highlighted in yellow) is quite large.
This ...
- 82k
10
votes
Why do motor drives have multiple bus capacitors of small value capacitance instead of a single bus capacitor of large value?
The capacitors help in filtering and decoupling noise. But each single value of capacitor is only good at one particular frequency. It has least ESR (higher ability to mitigate noise) Using a range of ...
- 9,461
8
votes
Why do motor drives have multiple bus capacitors of small value capacitance instead of a single bus capacitor of large value?
This could also be a production optimization thing. If a product already uses 220uF capacitors, using them instead of an additional 4700uF may make sense (though replacing one cap with 20 seems a bit ...
- 26k
8
votes
What does a "fork" symbol mean on a schematic?
It actually does seem like a relatively appropriate use of "chassis" ground. In the datasheet you linked to:
Note: Please solder the corner pad and the bottom thermal pad of the QFN package ...
- 663
7
votes
Why do we use capacitors in parallel with DC motors?
Your question is probably only answerable through context; you're right, instead of C2 and C6, everyone would expect flyback diodes, forming a ground path for voltage spikes that happen upon switching ...
- 100k
7
votes
What does a "fork" symbol mean on a schematic?
That is one of several symbols that may be used to indicate "Ground". I have seen lists defining specific applications for each symbol, but most often the different symbols seem to be used ...
- 60.8k
6
votes
Failing diodes and shorting NMOS and PMOS in H-bridge at 19A
Three problems:
1N4004 is rated to 1A, not 20A. And it is too slow.
You can use the FET body diodes instead. They should not conduct often if the FETs are driven synchronously, so there should be no ...
- 82k
6
votes
Accepted
How to improve efficiency of a "dead simple" motor driver - are more MOSFETs better or not?
Ideally, you want conduction losses to equal switching losses. But conduction and switching losses change with load (ala duty cycle) so the crossover point where switching losses = conduction losses ...
- 57.3k
5
votes
Why does my MIC4605 keep blowing up?
I had a lot of problems with that driver. After securing it in the following way, the device started to work properly:
Between MCU and driver inputs (in your case PWM and LSEN) I have added current ...
- 327
5
votes
Can we or should we parallel H-bridge module for increse current?
It is bad practice to blindly parallel drivers without knowing how to estimate the power dissipation and heat rise.
Generally you choose drivers and heatsinks so that they are capable of driving the ...
- 148k
4
votes
Accepted
Not able to power motor with the L298N motor driver
The PP3 9 V batteries you use are only suitable for loads that pull very small currents; they are nowhere near powerful enough to supply your motors (unless your motors are really tiny and pull ...
- 9,310
4
votes
Accepted
How does an H-bridge motor driver step down voltage and increase current?
Think first of a step-down DCDC converter. At its output, it consists of two switches (one to supply; one to ground) and an inductor.
When an inductor is carrying a current, it stores energy. When the ...
- 20.4k
4
votes
Understanding a SMD Motor driver IC (heat dissipation and control)
Is it compatible with the 3.3V micro controller?
What a poor data sheet! Are logic levels independent of Vcc? It is likely that logic low is compatible with a 3.3V micro controller. But what about ...
- 27.7k
3
votes
Why does my MIC4605 keep blowing up?
MOSFET gate drivers can oscillate, given the high power gain and unavoidable GND pin inductances.
Additionally the GND pin can have enormous swings above and below Ground. Unless the ESD structures ...
- 35k
3
votes
Why does my MIC4605 keep blowing up?
During tests with real hardware, either the MICs or the 5 ohm
resistors kept blowing up
This is not surprising, since the 5 Ω resistor should not be there. MIC4102 datasheet says:-
Current ...
- 57k
3
votes
How do I convert a PWM signal (with a specific duty cycle) to its respective analog value, for an application in a low voltage, high current circuit?
This seems like a case of the XY problem. I think you would be better served asking for what you really want, a 16V 50A supply for a tethered drone, rather than asking for how to adapt an entirely ...
- 71
3
votes
Accepted
Problems with dc motor driver design: Mosfet fail
One huge issue I'm seeing is a lack of any flyback diode for the motor. You need to add a high current diode from the mosfet drains to battery positive. This will give that energy somewhere to go. You'...
- 7,636
3
votes
Why do motor drives have multiple bus capacitors of small value capacitance instead of a single bus capacitor of large value?
A single, custom capacitor optimized for the needs of that drive would probably have some advantages, if that was the only product you were building. But if you build dozens of different drives, as ...
- 17.7k
3
votes
How to amplify 3.3 volts PWM to 5 volts PWM
You should specifiy your maximum PWM frequency.
The switching speed of the circuit below is likely to be fast enough for most Arduino or Pi PWM applications.
Here is a simple and slightly unusual ...
- 152k
Only top scored, non community-wiki answers of a minimum length are eligible