Crest PWC05041 (Cixi Yidong Electronics TA‑7)
Posted: February 19th, 2023, 8:03 am
another weird screw type (with 3 slots in a triangular formation at the perimeter), but my divided‑blade screwdriver (out of which I cut the notch myself) engaged them anyway .
Switching is double pole using two red microswitches rated for 16(2)A 250V. Their only steel part is the dummy (normally closed) contact, which is OK by me. (You'd think they could have announced double-pole switching as some other brands do, but now you know anyway.) Being two separate switches (with independent snap actions) does theoretically raise a concern that one could switch on some time before the other, but when I tested it they do click on in tandem. These are branded Cixi Yidong Electronic Co., Ltd, which indeed manufactures the whole device (it looks nigh-identical to model TA‑7 here, although searching the approval number instead gives results mostly of the form *TA‑14). The load wires are spot‑welded to their terminals, only the motor and LED connections are soldered here (very shiny solder though). The timer mechanism is unremarkable, using a typical teeny 10-pole (600RPM at 50Hz) synchronous motor of minimalist design (omitting 4 poles from the stator) with a gearbox.
The LED series resistor is 100kΩ ±5%, but there's no rectifying diode so it will dissipate 576mW at 240V (typical) or 734mW at 264V and −5% tolerance (worst case); the resistor is accordingly 1W judging by its dimensions (11mm long, 3.6mm diameter), although it will get hotter than comfortable for the (ABS?) housing so would have been more-appropriate with the rectifier. Also, it actually measures 110kΩ so must be mismarked (I've verified my DMM against spare 100kΩ ±1% metal film resistors), not that this relatively-minor error would do any damage. The input measures 54.4kΩ across, which comes from a 51kΩ ±5% 2W (15mm long by 4.8mm diameter) resistor (measures 50kΩ) in series with the motor coil (4.39kΩ cold); this resistor will get moderately warm, dissipating 723mW typical (at 240V assuming the motor is 48V) up to 921mW at 264V and −5% tolerance, but nothing tragic.
59mm wide at the plug/socket portion, the unit won't fit beside a plug in a normal outlet but does fit comfortably in the end socket on Crest's power‑boards, which is more than I can say for some other time switches (Arlec PC844, Kambrook KD84) with large square or rectangular bodies (71mm and 69mm wide respectively).
That just leaves a load test: Since the switches are 16A rated I applied that straight away; it got quite hot, but survived alright so 10A will be fine.
Conclusion
It was close to being decent, but the missing rectifier in the LED circuit lets it down. No worries, I have plenty of 1N4007s which I can add myself…
UPDATE 2023-03-01: Jackson Industries also sell it as the PTT1155 (despite being Crest's competitor otherwise), so you might as well have their lower price.
Superficially, it's your standard 24‑hour rotary time switch with on/off tabs per 15 minutes. They tried to keep me out with yet Switching is double pole using two red microswitches rated for 16(2)A 250V. Their only steel part is the dummy (normally closed) contact, which is OK by me. (You'd think they could have announced double-pole switching as some other brands do, but now you know anyway.) Being two separate switches (with independent snap actions) does theoretically raise a concern that one could switch on some time before the other, but when I tested it they do click on in tandem. These are branded Cixi Yidong Electronic Co., Ltd, which indeed manufactures the whole device (it looks nigh-identical to model TA‑7 here, although searching the approval number instead gives results mostly of the form *TA‑14). The load wires are spot‑welded to their terminals, only the motor and LED connections are soldered here (very shiny solder though). The timer mechanism is unremarkable, using a typical teeny 10-pole (600RPM at 50Hz) synchronous motor of minimalist design (omitting 4 poles from the stator) with a gearbox.
The LED series resistor is 100kΩ ±5%, but there's no rectifying diode so it will dissipate 576mW at 240V (typical) or 734mW at 264V and −5% tolerance (worst case); the resistor is accordingly 1W judging by its dimensions (11mm long, 3.6mm diameter), although it will get hotter than comfortable for the (ABS?) housing so would have been more-appropriate with the rectifier. Also, it actually measures 110kΩ so must be mismarked (I've verified my DMM against spare 100kΩ ±1% metal film resistors), not that this relatively-minor error would do any damage. The input measures 54.4kΩ across, which comes from a 51kΩ ±5% 2W (15mm long by 4.8mm diameter) resistor (measures 50kΩ) in series with the motor coil (4.39kΩ cold); this resistor will get moderately warm, dissipating 723mW typical (at 240V assuming the motor is 48V) up to 921mW at 264V and −5% tolerance, but nothing tragic.
59mm wide at the plug/socket portion, the unit won't fit beside a plug in a normal outlet but does fit comfortably in the end socket on Crest's power‑boards, which is more than I can say for some other time switches (Arlec PC844, Kambrook KD84) with large square or rectangular bodies (71mm and 69mm wide respectively).
That just leaves a load test: Since the switches are 16A rated I applied that straight away; it got quite hot, but survived alright so 10A will be fine.
Conclusion
It was close to being decent, but the missing rectifier in the LED circuit lets it down. No worries, I have plenty of 1N4007s which I can add myself…
UPDATE 2023-03-01: Jackson Industries also sell it as the PTT1155 (despite being Crest's competitor otherwise), so you might as well have their lower price.