Re: Master Clock contact spark quenching


Darren - i am still buying electronic supplies from China, and turnaround is a few weeks. If the value is low, then GST is not an issue - so far anyway.
Neil Jepsen. B.Sc. M.Sc(Hons).CPL.MASNZ.
Jepsen Acoustics & Electronics Ltd
22 Domain Street
Palmerston North.
New Zealand.
Ph +64 6 3577539  Mob 0274428094
Web site:
E.& O.E.
On 6/01/2021 11:55 am, Tony Nixon wrote:

I am really surprised that the delivery time from China to NZ is so long.  I have been buying Arduino and other small electronic parts from China using ebay for the last 5 years, generally keeping orders below GBP10 to avoid attracting duty.  Delivery has usually been 2-3 weeks (and free too!)  Most of the same parts can also be purchased from UK suppliers on a weeks turn round but at about double the price.  Are there no similar suppliers in NZ?

I have noticed in the last two months though that free delivery seems to be disappearing, I read somewhere that some concessionary deals offerd to the Chinese for cheap shipment have now ended.  A more worrying development that I have just started to hear about is that post Brenxit the UK is apparently going to require all suppliers selling into the UK to register to pay VAT with the UK authorities.  One European supplier (of bike parts) has apparently already decided no longer to deal with customers in the UK.

I am just beginning to experiment with an ESP8266 Node MCU to get a time stamp from NTP to log temperature, pressure and error on my Pulsynetic.


On 5 Jan 2021, at 19:48, Darren Conway <darren.conway@...> wrote:


Here is a Aduino  Motor shield that would be ideal for driving the Gents and Solari slave  clocks. 


Darren Conway
36 Orr Crescent
Lower Hutt
New Zealand
ph +64  (0)4 569 1963

On 6.01.21 7:12 am, Darren Conway wrote:


If I only had to drive slaves from the Synchronome, an opto isolator would be the obvious choice.  I already have one.

An Aduino with ready made shield is probably the easiest way to convert a 30 second pulse to a one minute bipolar drive for the flip clock.  Easier than building from discrete components.  If I do that, then using the Aduino as an electronic relay to drive the slave clocks would make sense.

I am thinking of using a cheap Chinese motor/power switch shield with an Aduino to generate the bipolar drive for the flip clock.   Generating a bipolar signal requires and H driver circuit, as used to drive stepper motors or DC motors.   If I get a Auduino wifi version, there is the potential to use an on-line NTP server as the master clock, complete with automatic daylight time corrections.    The only problem is that shipping times from China are currently about 3 to 6 months.

The master still needs to drive its own solenoid coil and case fitted slave, so a snubber circuit would still serve a purpose.


Darren Conway
New Zealand

On 5.01.21 10:54 pm, John Haine wrote:
That's because it's opto isolated, it needs a current of ~3 mA into the input pin to light up the internal LED, so you drive it through a suitable resistor to get that current from whatever voltage is across the contacts.  In this case with 12 V that would be 12/3 = 4 K ohms, or 3.9 K NPV. 


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