blue arrow (can); red arrow (chip)
Blue arrow: crystal
Red arrow: some sort of IC or microcontroller
Blue could be a receiver, resistor, transistor or rectifier.
Red is a 555 timer.
Blue is definitely a 4MHz crystal oscillator
Not sure on red. Package size isn’t right for a 555 or 556. Are there any package markings under that sticker?
Blue arrow: A quartz crystal like this: http://www.digikey.com/product-detail/en/ecs-inc/ECS-40-18-4XEN/XC1735-ND/2213755
With 20 pins?
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The 1st one is a 4 Mhz crystal oscillator
The 2nd one … I’m not sure … but it looks like a PWM clocking chip, probably similar to a TI555
What purpose would the oscillator serve with the 555 (or 556) chip? None of the DIY 555-based PWM circuits I have seen incorporate a crystal oscillator.
80% sure the device is a E-Sky servo tester http://www.hobby-wing.com/e-sky-servo-adjuster---tester---ek2-0907.html
pinout and layout matches.
1st is a 4 mhz crystal oscillator
Chip is tricky. Knowing Ether it’s probably a analog IC but knowing China it’s probably a dedicated no name IC designed for servo testers. A bunch of pins are left unused and tied to ground even though no significant current is being passed through them which could mean A: additional functionality is unused like a sweep mode that’s common on other testers or B: The manufacturer is using a common size package for the dedicated chip because it’s cheaper to manufacture that way.
Crystal oscillator leans me towards a dedicated hardcoded microcontroller IC, very likely that no easily available datasheet exists for it.
Well, it’s hard to tell, but with that VR (variable resistor) sitting in the middle of it I’d have to guess that it is a light dimmer of some sort.
Where did it come from? Something laying around or off an old robot?
My guess would be it replaces R1 and C1 in This 555 PWM timer.
It would be used to clock the square wave, where the pot would be used to adjust the on/off time.
the bue is a 4mhz crystal… which indicates that the red IC must be a microcontroller dedicated for PWM generation… Capacitors and resistors used for filtering nosise and zenner diode (ZD1) for voltage regulation.
The first one is a variable electronic oscillator circuit. The second one, I’m guessing, is the modern IC equivalent… something like a counter/divider oscillator chip…
But then again, me mechanical, electrical scary…
Does the (33) sticker? come easily off the chip?
Here’s a DIY 555/556 based PWM signal generator circuit that Don Rotolo posted on CD 12 years ago. The only external components are resistors and capacitors. There is no crystal oscillator.
Does the 4MHz crystal oscillator make the circuit superior in any way?
I’d wager the crystal is just there to meet the minimum radiated EMI requirement for a cheap Chinese electronic doohickey. :rolleyes:
I’d bet a donut that mman1506 has it right though; the IC is probably a multi-function chip that’s as cheap/easy to implement as a simpler option. The same outfit probably makes a more advanced servo tester and they got a good price break on the IC, so they tossed it onto another board that would occupy a different price/market segment. Even if the cost of the IC and crystal come out a little higher then the parts needed for the barest functionality, they might still save money and time laying out, printing and assembling the boards.
Consumer electronics manufacturing logistics are weird.
I can basically confirm the chip is a MCU. The product is also sold as"MCU control 000504"](https://www.aliexpress.com/store/product/VATI-MCU-Control-000504-EK2-0907-Servo-Tester-Adjuster-for-RC-Helicopter-Honey-Bee/825837_32291655964.html) and the descriptions usually advertise it’s use of a microcontroller. Also the 4mhz crystal oscillator is connected in a way that’s typical of a MCU like a Atmega Attiny. I’d bet the original prototype of the device used a low power Atmega or PIC and then it was given to a IC manufacturer who hard coded it into a production run of a standard MCU that they manufacture for high quantity low cost devices like these. I can’t seem to find a brand name MCU with this exact pinout so it’s probably a no name.
EDIT: Pretty sure it’s a PIC16F84A or a knockoff of one
Here’s a bottom view and a side view of the guts of a unit I bought on eBay for $2.65 (that price included free shipping).
The bottom view shows an unnamed chip with 14 pins (same as a 556; coincidence?) and an SS32 Schottky Barrier Rectifier.
The side view shows what looks to be a crystal oscillator, like the blue arrow pic in the OP.
Is it likely that the 14 pin chip is an MCU and not a 556?
That’s the updated version of your other one usually called the “EK2-0907”. Considering it has sweep functionality it’s very likely it also has a MCU. Those unbranded 14 pin MCU chips are very common on Chinese devices, you can send someone your PIC code, they will port it to assembly and send you back tons of them ready to go for almost nothing. It’s probably based on the PIC16F676-I/SL in a SOP14 package.
If reverse engineering electronics is something that you enjoy, you might like bunnie’s blog. He runs a monthly competition where he posts a closeup of a circuit board and people try to guess what it is.