Hardware Is Hard?(prdpx7.github.io)
prdpx7.github.io
Hardware Is Hard?
https://prdpx7.github.io/posts/hardware-is-hard/
12 comments
Thoughts as a computer engineer:
1. The motor demo didn't work for me (Firefox on Android). Nice to say it was made by Claude.
2. Voltage isn't like gravity. It's literally called potential. Voltage is the water being high up on the mountain. Gravity is the gravity, which was kinda the point of the analogy, no?
3. A Tesla has thousands not hundreds of 18650s. But I guess that's a superset.
4. For motor speed, I would use P = I x V. It shows the way the two work better, and the resulting P = I^2 x R = V^2 / R. Resistance is constant.
5. PWM wasn't explained right here. You can most certainly vary the voltage without PWM, and it's not just any old modulation you want. You want a binary output so your transistors don't go linear, and you can control the average power. PWM is easy for linear scaling. But you could presumably use other modulations.
6. It's important to understand what the H bridge is doing, why it matters, and what it offers. Shoot through and dead time are important. Understanding that the microcontroller outputs X current at Y voltage, and the motor needs J current at K voltage. You could drive a small enough motor directly.
7. Could maybe do a 2-cell charger with balance leads as a usability upgrade.
8. The 2 cells in series is upwards of 8.4v which is higher than the 5.5v that USB related chips allow and 6v that their absolute max is. Would be good to understand what the power chain is to make sure nothing blows up.
I think this is a good start and always kudos to those who learn, even more to this trying to teach others. Hopefully there's a part 2 going into more very simple theory. Especially a comparison vs the L298N.
1. The motor demo didn't work for me (Firefox on Android). Nice to say it was made by Claude.
2. Voltage isn't like gravity. It's literally called potential. Voltage is the water being high up on the mountain. Gravity is the gravity, which was kinda the point of the analogy, no?
3. A Tesla has thousands not hundreds of 18650s. But I guess that's a superset.
4. For motor speed, I would use P = I x V. It shows the way the two work better, and the resulting P = I^2 x R = V^2 / R. Resistance is constant.
5. PWM wasn't explained right here. You can most certainly vary the voltage without PWM, and it's not just any old modulation you want. You want a binary output so your transistors don't go linear, and you can control the average power. PWM is easy for linear scaling. But you could presumably use other modulations.
6. It's important to understand what the H bridge is doing, why it matters, and what it offers. Shoot through and dead time are important. Understanding that the microcontroller outputs X current at Y voltage, and the motor needs J current at K voltage. You could drive a small enough motor directly.
7. Could maybe do a 2-cell charger with balance leads as a usability upgrade.
8. The 2 cells in series is upwards of 8.4v which is higher than the 5.5v that USB related chips allow and 6v that their absolute max is. Would be good to understand what the power chain is to make sure nothing blows up.
I think this is a good start and always kudos to those who learn, even more to this trying to teach others. Hopefully there's a part 2 going into more very simple theory. Especially a comparison vs the L298N.
2. It's a good analogy. Waterfall are falling because of gravitational potential energy, just like an electron would fall when put in an electric field.
At constant height, a dam on the moon have less potential energy than an actual dam.
And gravity is a potential: https://en.wikipedia.org/wiki/Gravitational_potential "It is analogous to the electric potential with mass playing the role of charge."
At constant height, a dam on the moon have less potential energy than an actual dam.
And gravity is a potential: https://en.wikipedia.org/wiki/Gravitational_potential "It is analogous to the electric potential with mass playing the role of charge."
If you read the Wikipedia you linked you'll see that gravitational potential != gravity. So no. If the author had said voltage is analogous to gravitational potential, sure. But they didn't. They said gravity. Here's the page for gravity: https://en.wikipedia.org/wiki/Gravity which brings with stating gravity is a force. Not a potential.
>1. The motor demo didn't work for me (Firefox on Android). Nice to say it was made by Claude.
oh! i did tested on firefox with different devices on my laptop. but not in actual android phone. thanks for flagging it
>2. Voltage isn't like gravity. It's literally called potential. Voltage is the water being high up on the mountain. Gravity is the gravity, which was kinda the point of the analogy, no?
yeah! my bad. i might have wrote few things when i was just reading up and writing as i am trying to internalize what all these things mean
>5. PWM wasn't explained right here. You can most certainly vary the voltage without PWM, and it's not just any old modulation you want. You want a binary output so your transistors don't go linear, and you can control the average power. PWM is easy for linear scaling. But you could presumably use other modulations.
there are probably 10 more ways to make voltage dance - and i only read about two. one is resistors and other is PWM.
>Would be good to understand what the power chain is to make sure nothing blows up.
The blog has link which points to exact wiring instructions including adding buck converter. again! the purpose of this blog is not to explain every bit in detail. it's about what i have learned - because before doing all of this - i had zero clue about everything
oh! i did tested on firefox with different devices on my laptop. but not in actual android phone. thanks for flagging it
>2. Voltage isn't like gravity. It's literally called potential. Voltage is the water being high up on the mountain. Gravity is the gravity, which was kinda the point of the analogy, no?
yeah! my bad. i might have wrote few things when i was just reading up and writing as i am trying to internalize what all these things mean
>5. PWM wasn't explained right here. You can most certainly vary the voltage without PWM, and it's not just any old modulation you want. You want a binary output so your transistors don't go linear, and you can control the average power. PWM is easy for linear scaling. But you could presumably use other modulations.
there are probably 10 more ways to make voltage dance - and i only read about two. one is resistors and other is PWM.
>Would be good to understand what the power chain is to make sure nothing blows up.
The blog has link which points to exact wiring instructions including adding buck converter. again! the purpose of this blog is not to explain every bit in detail. it's about what i have learned - because before doing all of this - i had zero clue about everything
I don't think you understand the point of PWM then which is ok. A resistor wouldn't provide runtime control of the power going to the motor, unless you had a programmable resistor which would likely explode from the current induced heating. And that's fine, because everybody just uses PWM, but if you do a follow-up I recommend investigating why the motor is connected and controlled in the way you did it.
Depends what you are doing. Digital circuits are not really that hard. You are just repeating known patterns and keeping the voltage in correct level (3V3, 5V, ...) unless you are doing some bleeding edge stuff in GHz range. And because these circuits are very deterministic it is also simple to emulate them down to the transistor
Analogue circuits on the other hand are massive PITA. They have their own mind, reacting to the smallest of fields and very hard to work with.
Analogue circuits on the other hand are massive PITA. They have their own mind, reacting to the smallest of fields and very hard to work with.
haha! i am just starting up. will see how the journey goes.
thanks for the heads-up about analouge circuits
I would say this reading took a sharp turn from what I expected on the title, but it does make sense. There is plenty of hopeful potential in this type of public learning. The author starts off with wild intentions and eventually practically works out a solution, even though you can tell it was not quite what was envisioned.
That happens to me too, I start doing something and a result isn't the end of the learning, but a chance to repeat the experience.
That happens to me too, I start doing something and a result isn't the end of the learning, but a chance to repeat the experience.
Hardware is slow
We had both played with a bit of arduino or hobbyist stuff in the past, but dove right into EEG and neurostimulation.
Hardware is hard like software used to be hard. When we think of hardware, we're usually caught up just in the electrical chip, transistor, firmware, IO mentality.
Maybe it's just because of what we're building (https://affectablesleep.comm) but we also have to factor in mechanical design, electrical/mechanical interfaces, material science (electrode sensors), etc.
I've learned power management isn't always about, how long does my battery last, but also, how do micro-fluctuations in voltage during use impact other sensors or other operating systems.
Hardware, for us at least, has been a significantly larger footprint than we initially would have expected. It isn't just hardware, firmware, control app. For us it's been the above, plus data-quality tooling, firmware CI, in-factory provisioning and security, the list seems to go on and on.
It's a new challenge, and has been a very fun one. It does remind me a bit of the early days of the web when we'd write our own web-server, DB connection logic, etc etc.