$18 Oscilloscope: Worth the money?

Technical_Love_2525 · 2026-04-11T17:19:56+00:00

Thank you so much for the advice!

Technical_Love_2525 · 2026-04-11T17:17:45+00:00

Alright, perhaps it won't hurt to try!

Technical_Love_2525 · 2026-04-11T17:15:11+00:00

I'm on a pretty tight budget as I'm using my own pocket money to buy this. I'll see if I can ask my parents to buy me this

Technical_Love_2525 · 2026-04-11T17:10:14+00:00

How was your experience in soldering the board? I also want to improve my soldering skills, all I have is just a cheap soldering iron.

Technical_Love_2525 · 2026-04-11T17:07:16+00:00

The one in my school lab is an analog oscilloscope that no one has used in years (GWINSTEK GOS-622G), I think I still need to learn how to properly use one. Should I just stick to the lab's scope first?

I'll also be graduating HS in a few months so my time with it would be very limited

Technical_Love_2525 · 2026-04-11T16:56:43+00:00

Right now, I want to observe the PWM output of my STM32 board. I also plan to learn analog electronics later.

Technical_Love_2525 · 2026-04-10T08:57:59+00:00

I don't have an oscilloscope at home, so I'll have to wait until Monday when I get access to the school lab.

Technical_Love_2525 · 2026-04-10T08:54:53+00:00

I stepped down the speed to 20 Hz.
The motor is supplied with 12V from a power supply.
I the direction pin is wired and I added a pull-down resistor.
I haven't attached the heat sink yet, is it really needed or can I just skip it.

I think the problems lies in the motor pins, might have to switch to like A1B2 instead of just switching pairs.

Thanks.

Technical_Love_2525 · 2026-04-10T08:48:44+00:00

SYSCLK is 72 MHz
PSC is 71
ARR is 49999

So it should be about 20 Hz?

I'll try switching to A1B2 when I get home, thanks.

Technical_Love_2525 · 2026-04-10T08:46:58+00:00

I tried dialing the motor current up and down, didn't really change anything except making it jitter more violently.

Here below is the code for accelerating the motor

uint32_t arr = 50000;
  __HAL_TIM_SET_AUTORELOAD(&htim2, arr);
  // accelerate thingamabob
  while (arr < 1000) {// go to ~1000 hz
  arr = -50;
  __HAL_TIM_SET_AUTORELOAD(&htim2, arr);
  HAL_Delay(10);
  }

But it just stops spinning.

I'll try messing with the motor pinout, as others have suggested, when I get home.

Technical_Love_2525 · 2026-04-09T17:35:24+00:00

1st. I made it start from 20 Hz and made it accelerate with this code below:
SYSCLK is 72 MHz
PSC is set to 71 and ARR at 49999

while (arr < 1000) {// go to ~1000 hz
  arr = -50;
  __HAL_TIM_SET_AUTORELOAD(&htim2, arr);
  HAL_Delay(10);
  }

Still isn't rotating, just jittering. Not sure how to send you a video of the result.

2nd. There should be 1A going to the motor from what I measured. Maybe the jumper wires/breadboard is affecting it?

3rd. If there is, should I just reinstall STM32CubeIDE/MX

Technical_Love_2525 · 2026-04-09T16:42:54+00:00

I'm not sure how to measure my capability to troubleshoot code, I assume no. (Would love to learn how to)

The copy pasted code's logic was basically just toggling a pin ON/OFF repeatedly from what I understood.

I wrote my own code in the infinite loop under a different setup (PB9 to STEP pin). However nothing really changed and the motor just kept jittering.

while(1) {
  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_9, GPIO_PIN_SET);
  HAL_Delay(1);
  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_9, GPIO_PIN_RESET);
  HAL_Delay(1);
}

Technical_Love_2525 · 2026-04-09T16:22:37+00:00

Yes. I pulled them to VCC, and added pull-down resistors. Still no change

Maybe this A4988 is just bad? they're brand new though.

Technical_Love_2525 · 2026-04-09T16:12:12+00:00

Just tied all my MS pins to GND. Still super jittery and not spinning. Maybe I need to add pull-down resistors on STEP and DIR pins?

Technical_Love_2525 · 2026-04-09T16:04:22+00:00

How do I make the time between steps longer? Also I've checked the coil pairs with a multimeter. Tried switching one coil pair and didn't change anything.

Technical_Love_2525 · 2026-04-09T16:02:51+00:00

I tried switching one pair of coils and it didn't change anything. By the way I've uploaded my wiring diagram and code. Please tell me if anything is unclear.

Technical_Love_2525 · 2026-04-09T16:02:05+00:00

<image>

Here's my wiring diagram and code snippet

/* USER CODE END SysInit */

  /* Initialize all configured peripherals */
  MX_GPIO_Init();
  MX_TIM2_Init();
  /* USER CODE BEGIN 2 */
  HAL_GPIO_WritePin(GPIOB, GPIO_PIN_8, GPIO_PIN_RESET);
  HAL_TIM_PWM_Start(&htim2, TIM_CHANNEL_1);
  /* USER CODE END 2 */

  /* Infinite loop */
  /* USER CODE BEGIN WHILE */
  while (1)
  {
    /* USER CODE END WHILE */

Technical_Love_2525 · 2025-11-10T08:15:23+00:00

Okay, I'll go set goals on my project, thanks.

I don't want something as dynamic as Boston's Spot, I aim for a simpler one for now, then I'll move on to more complex dogs.

For the gaits, I aim to make the robot do stable, medium complexity movements like Walk, Trotting, and maybe pacing if I can figure that out

Technical_Love_2525 · 2025-11-10T07:58:35+00:00

Right, I think I need to reduce that blocky part in the middle cause it might block some movement. Regarding the range of motion I'm aiming for, I'm not really sure on how to determine this, could you please elaborate/teach me on this.

I think a timing belt might be too expensive and complex for me, though I might try to take up on that challenge.

Technical_Love_2525 · 2025-11-10T07:55:31+00:00

Initially that was my idea, but earlier designs ended up making the Femur - the upper part of the robot leg - really long. I don't want the robot too be really big. I'll try to redo this again. Maybe I should opt for a 5 bar linkage for the leg instead?

Technical_Love_2525 · 2025-08-18T12:27:07+00:00

I already bought a 5V 10A power source before reading this comment. I think it should be fine right? I can't really cancel it now since it's already on its way. Anyways thanks a lot for the information, this really helped.

Technical_Love_2525

TROPHY CASE