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I am trying to control a 4.5V motor with a pi.

I am going to use this to control the motor:
https://www.ebay.com/itm/2X-L298N-Dual-H-Bridge-DC-Stepper-Motor-Driver-Controller-Board-Arduino/382579265852?hash=item591380513c:g:oFoAAOSwszVbs4sl&frcectupt=true

The motor came with a meccano set, so all I know is that it is 4.5v (D469). The power supply I am planning on using:
https://www.ebay.com/itm/4-5V-Power-Supply-3-x-AAA-Battery-Holder-Enclosed-Case-Box-Switch-Wire-Lead-2pcs/322095307119?hash=item4afe60596f:g:9DwAAOSwjARcZO7w&frcectupt=true

do these two things have any incompatibilities with eachother or with a pi that I am not taking into account?

@Milliways Actually I am purposely not using the power supply/H bridge that came with the set to explore the pi. This power supply looks like it matches to me, am I wrong?

  • You haven't told us much about the motor (how many mA does it use). If it's small, 3 1.5V batteries should work; or a small ~4.5V power supply. – scitronboy Mar 28 at 23:52
  • Use a power supply that matches your motor! Preferably also use a controller designed for the Pi. – Milliways Mar 28 at 23:57
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Your eBay L298N motor driver and 4.5V power supply match each other.

Meccano 4.5V motors for road racers are usually heavy duty and take huge current.

If you have only one big Meccano motor, then I would recommend to get four small ones like those from Adafruit. Or you might like to show us a picture of your Meccano motor, just to make sure.

Reference Links

eBay L298N x2 Dual H Bridge DC Stepper Motor Driver Controller Board Arduino US$5.49

eBay 4.5V Power Supply 3 x AAA Battery Holder Enclosed Case Box Switch Wire Lead 2pcs -US$3.80

Meccano Off-Road Racer 25-in-1 Motorized Building Set

Adafruit DC Gearbox Motor - "TT Motor" - 200RPM - 3 to 6VDC US$2.95

AdaFruit DC Toy/Hobby Motor 130 Size US$1.95

These are standard '130 size' DC hobby motors. They come with a wider 
operating range than most toy motors: from 4.5 to 9VDC instead of 1.5-4.5V. 

Rated Voltage: 6.0VDC    
No-load Current: 70 mA max    
No-load Speed: 9100 ±1800 rpm    
Loaded Current: 250 mA max    
Loaded Speed: 4500 ±1500 rpm    
Starting Torque: 20 g*cm    
Starting Voltage: 2.0    
Stall Current: 500mA max

Adafruit TT Motor Description and technical data

Rated Voltage: 3~6V
Continuous No-Load Current: 150mA +/- 10%
Min. Operating Speed (3V): 90+/- 10% RPM
Min. Operating Speed (6V): 200+/- 10% RPM
Torque: 0.15Nm ~0.60Nm
Stall Torque (6V): 0.8kg.cm
Gear Ratio: 1:48
Body Dmensions: 70 x 22 x 18mm
Wires Length: 200mm & 28 AWG
Weight: 30.6g

3VDC   ~150mA 120 RPM no-load, 1.1A stall
4.5VDC ~155mA 185 RPM no-load, 1.2A stall
6VDC   ~160mA 250 RPM no-load, 1.5A stall

tlfong01's L298N motor driver and TT 3~6V motors

tlfong01's L298N testing notes

Update 2019apr05hkt2214

Motor Driver and Motor Compatibility Check

I checked the TT Motor at 4V5, and no load and stalled current to make sure the driver L298N DC current limit of 2A is not exceeded. The geared output shaft stalled (but non gear shaft still moving with slipped gear chain) shoots to over 250mA, but immediately returned to a stable value of about 130mA.

So far so good.

TT Motor Stall Current at 4.5V Vcc

I checked the stall current of the 130 motor without gearing, and found the stall current around 700mA. So a newbie like me should play with geared motor first, because the "stalled" current (when gear out stalled, but shaft still moving, with the gear chain slipping) is only around 140mA.

enter image description here

eBay AAA x3 = 4.5V Batteries Case with Switch Lead

The eBay Battery holder says "holder switch wire lead", but I don't see any switch on the holder. I usually use battery holders with a switch.

The manual switch is very useful when during testing you smell plastic burning, smoke coming out, motor finger burning hot etc, you can immediately switch off the battery. For the cheapy motors I am testing, I found them from time to time gets stalled because gears locked, and you need to start by turning it by hand. The stall current is many times than the steady current, so it is important to switch off the battery first.

battery case with switch

I also googled that Duracell 1.5V AAA battery can last about 1,000 mAh at 100mA load. So it should be OK to test the TT geared motors which consume of the order 100mA.

1.5V AAA Duracell Alkaline Battery Tests - RightBattery.com

– 970 mAh at 0.1A load
– 777 mAh at 0.2A load
– 553 mAh at 0.3A load
– 336 mAh at 0.5A load

The Meccano motor looks like a big guy. Its shaft looks like 5mm diameter. Let me find a similar motor and measure the current.

Meccano motor

I searched my junk box and found a big motor looking similar to the Meccanno motor. I has a 5mm diameter shaft. I measured its current with different voltages and summarized the results in the following picture.

meccanno motor spec

  • thanks! yeah you were right on, it is the motor in the Meccano Off-Road Racer 25-in-1 Motorized Building Set. So CAN I use that motor or do I HAVE TO buy smaller ones? Is the downside to using the 4.5v motor that I have that it will use up batteries quickly? – thecanmancan2 Apr 13 at 3:42
  • Can you show me a picture of your Meccano motor, or tell me how heavy it is? I have never seen any of those very expensive Meccano toys. All I know is from Google. I know it is 4.5V, but it might take huge current that L298N driver cannot support. You might also read how I am testing the cheapy motor raspberrypi.stackexchange.com/questions/95999/… – tlfong01 Apr 13 at 4:15
  • And this one - raspberrypi.stackexchange.com/questions/96258/… I am answering a couple of L298N motor drivers at the same time, and I often mixed up which questions I am doing. – tlfong01 Apr 13 at 4:23
  • Yes, I do worry that my very expensive Duracell cells are not that durable when playing with DC motors. So I have already bought some cheapy, fake 16450, lithium rechargeable batteries to test my motors. I read that Tesla Model S battery is actually made of several thousand those16450 cylindrical cells. So I think I should exit Duracell and enter the dragon, 16450. – tlfong01 Apr 13 at 4:32
  • The motor is already built into the car but here is a picture of it with my hand for scale: ibb.co/TvYmdJP I cannot find a picture of it by itself. Anyway, thank you for doing the testing, for any future projects I will use those smaller motors but meanwhile I see you mentioning the Amphere requirements a few times. How do I know what that is? I also see you mention that thing does not support that many amps or thing requires a certain number of amps. but I do not see that written anywhere. How do I find out those numbers? – thecanmancan2 Apr 15 at 23:13

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