FAQ
TL;DR: For that phone-charger circuit, 120 mA is the design current, and “Just about any medium power NPN transistor will do.” [Elektroda, Olin Lathrop, post #21659260]
Why it matters: This FAQ helps hobbyists quickly choose and source a safe, workable SL100 replacement for a mobile phone battery charger in the Philippines and beyond.
Quick Facts
- Design current: Approx. 120 mA; choose a package that can shed some heat. [Elektroda, Olin Lathrop, post #21659260]
- Suitable drop-in class: Medium-power NPN, TO‑220 form factor (e.g., TIP41 family). [Elektroda, Olin Lathrop, post #21659260]
- Part-number gotchas: Reported SL100 may be a typo or case-marking confusion. [Elektroda, David Deleonardo, post #21659255]
- Where to look up parts: alldatasheet and findchips were suggested by contributors. [Elektroda, Praveen Kumar Avala, post #21659252]
- Local sourcing tip: Ask shops for equivalents; CL100 was mentioned as a similar option. [Elektroda, Dennis Bauer, post #21659259]
What is the SL100 transistor, and is that part number correct?
Forum contributors suspected the “SL100” label might be a typo or a case-marking mix‑up. Before hunting parts, verify the schematic’s actual transistor requirements and part code. Cross‑checking the reference design or datasheet avoids buying the wrong device. When markings differ from full part numbers, sellers and catalogs can mislead. Confirm parameters first, then match with an equivalent, not the marking alone. [Elektroda, David Deleonardo, post #21659255]
What can I use instead of an SL100 in the EFY mobile charger?
Use a medium‑power NPN transistor that can dissipate modest heat. The charger limits current to about 120 mA, so the job is undemanding. A general‑purpose TO‑220 NPN works well here. TIP41 is a convenient choice kept by many builders for such roles. Select a heat‑capable package rather than tiny small‑signal devices. "Just about any medium power NPN transistor will do there." [Elektroda, Olin Lathrop, post #21659260]
Will a TIP41 work for this battery‑charger project?
Yes. TIP41 BJTs are common, versatile, and available from many manufacturers. That breadth helps sourcing in local markets. One contributor highlighted using TIP41s in labs and projects due to ubiquity. If you pick a TIP41, still confirm pinout and basic specs against your circuit. This avoids wiring errors and overheating. A note from experience: lead‑free variants are replacing older versions in many catalogs. [Elektroda, Alec, post #21659261]
Which parameters actually matter when choosing a substitute?
Focus on current handling, power dissipation, and package. The circuit’s current is limited to about 120 mA, so thermal needs are modest. Choose a package with some heat capacity, like TO‑220. Voltage ratings and gain should meet or exceed the design’s needs, but extremes are unnecessary here. Matching only the essential parameters keeps sourcing flexible and reliable. [Elektroda, Olin Lathrop, post #21659260]
Where can I find datasheets or check availability fast?
Use online aggregators mentioned by contributors: alldatasheet for specifications and findchips for distributor stock snapshots. These tools help confirm key parameters and identify stocking equivalents. Search by function and package if the original part number is unclear. Then shortlist available medium‑power NPNs for your region. [Elektroda, Praveen Kumar Avala, post #21659252]
Can a shop suggest an equivalent, like CL100, if SL100 isn’t available?
Yes. Bring your schematic and required specs. Local electronics sellers can propose close equivalents, such as CL100, that fit your application. This is practical when inventories differ across regions. Still verify the substitute’s pinout, package, and ratings before purchase. Ask for a quick datasheet printout or QR link to confirm. [Elektroda, Dennis Bauer, post #21659259]
How do I pick a substitute transistor quickly? (3‑step)
- Note required current (~120 mA) and pick a heat‑capable package.
- Choose a medium‑power NPN in TO‑220 (e.g., TIP41 class).
- Verify voltage, gain, and pinout match your layout before soldering.
[Elektroda, Olin Lathrop, post #21659260]
What happens if I drop in a small‑signal NPN instead?
Small‑signal packages lack thermal headroom. Even at 120 mA, they can overheat or fail during charging. The design benefits from a package that can dissipate some heat. Use a medium‑power device to keep junction temperatures reasonable and extend life. This prevents erratic charging or thermal shutdowns. [Elektroda, Olin Lathrop, post #21659260]
Why might TIP41 be a poor choice for a low‑dropout regulator build?
A contributor noted TIP41’s VCE(sat) is not ideal for very low‑dropout linear regulators. That edge case can cause excessive dropout and heat at low headroom. For LDO roles, select a transistor or regulator with lower saturation or use a dedicated LDO IC. “Vce saturation spec not so awesome for that application.” [Elektroda, Alec, post #21659261]
Do I really need to list every parameter to find an equivalent?
No. Designers rarely operate at every parameter’s limit. Identify which parameters your circuit truly uses, then meet or exceed those. This approach simplifies substitution while keeping the design safe. It also broadens your sourcing options when the exact part is missing. [Elektroda, Olin Lathrop, post #21659256]
What is Arduino Nano?
Arduino Nano is a compact microcontroller board compatible with Arduino IDE, often used for small embedded projects and quick prototypes. It includes USB programming, multiple I/O pins, and supports shields and libraries in the Arduino ecosystem. It suits breadboards and tight spaces. Check voltage levels and current limits when interfacing with power circuits. [Arduino Nano]
What is CAN bus?
Controller Area Network (CAN bus) is a robust serial network for reliable communication between microcontrollers and devices, common in vehicles and industrial systems. It uses differential signaling, arbitration for message priority, and strong error handling. It enables distributed control without a central computer. Use transceivers to connect MCUs to the bus lines. [Controller Area Network]
What is Tuya?
Tuya is a smart‑home IoT platform that provides cloud services, mobile apps, and firmware for connected devices. Brands use Tuya modules to speed time‑to‑market. Users link devices via the Tuya or Smart Life apps. Developers can integrate through Tuya’s cloud APIs and SDKs. [Tuya Smart]
What is OpenBeken?
OpenBeken is open‑source firmware for certain Wi‑Fi IoT modules, used to replace stock cloud firmware with local control. It targets devices using specific chipsets and enables MQTT, rules, and web UI management. Always confirm module compatibility before flashing. Backup factory firmware when possible. [OpenBeken]
