Not able to levitate magnet for magnetic levitation project

Question

I am following a hackster project on magnetic levitation here - https://www.hackster.io/jsirgado/magnet-levitation-with-arduino-eeeee4

However, I have followed everything but still, it's not working.

Here are changes to the circuit I made:

1. The electromagnet which I am using is that of 5V instead of 12V
2. The transducer which I am using is ss8050 instead of TIP120
3. Hall sensor is tapped just at the bottom of the electromagnet

Electromagnet link - https://shop.edwinrobotics.com/widgets/1568-5v-electromagnet-25-kg-holding-force-p4020.html

Update:-

The best I can do is to make the magnet jump up and down fast but it never levitates. Have tried changing PID setting from the project as aggressive and mild but still didn't achieve the final result.

I need advice from an expert to tell me what I am doing wrong here. All components are in good condition and 5v electromagnet is strong enough.

So what am I missing here?

Answer 1

All CMOS drivers have an Ron resistance with a wide tolerance, for Vout="1","0"

\$ ~~~R_{on}=\frac{(Vdd-Voh)}{Iol} ,\frac{V_{ol}}{I_{ol}}\$ 3.3V logic family is 25 Ω, and 5V logic family is 50 Ω ±50%

\$I_b=\frac{(V_{dd}-V_{be})}{\frac{(Vdd-Voh)}{Iol}+R_s}\$

- if using 3.3V logic which is a 25 Ohm driver
- to NPN @ 60 mA base current with specs of VBE(sat)=1.2V @ 80mA, Vbe (on)= 1V @ 10mA
- Choose Rs = 10 Ohms from 60mA=(3.3V-1.2V)/(Ron+Rs) 2.1V/60mA=35 Ohms
- driver Pd= 60mA*3.3V = 200mW shared by driver, Rs and Vbe

- if using 5V logic which is Ron= 50 Ohm driver
- Choose Rs = 13 Ohm from 60mA=(Vdd-Vbe)/(Ron+Rs)

^{simulate this circuit – Schematic created using CircuitLab}