# Circuitry for striking clock.

#### RMHC

Joined Nov 13, 2019
45
I wish to make a striking clock using the following- 1. Quartz clock movement (1.5v.) with hourly trigger switch. 2. Solenoid working on 6v. with 10.5 ohm coil which includes a spring loaded plunger to hit the gong. I have a block diagram for reference on the attached files.
I really appreciate any help with the circuit and hope that a member is interested in helping. Many thanks. RMHC.

#### crutschow

Joined Mar 14, 2008
25,263
This appears to be homework.
So we need to see some effort from you as to your initial thoughts on how to generate the required pulse to the solenoid.
You can start by drawing a block diagram of the proposed circuit.

#### RMHC

Joined Nov 13, 2019
45
This appears to be homework.
So we need to see some effort from you as to your initial thoughts on how to generate the required pulse to the solenoid.
You can start by drawing a block diagram of the proposed circuit.
crutschow,
Thanks for the reply. I would have no difficulty with this circuit were it not for the fact that the solenoid requires a single pulse, as opposed to a sustained 'ON' for 2 minutes which the clock provides. I would use a miniature relay triggered by the clock contact to switch 6v. to the coil. Easy to do. My hang-up is generating a short pulse from the trigger signal. Thanks for your further help. RMHC.

#### DNA Robotics

Joined Jun 13, 2014
571
Use a 1 megaohm resistor to charge a capacitor to 6 volts.
Use the trigger to turn on a transistor that will dump the capacitor charge into the solenoid.

#### crutschow

Joined Mar 14, 2008
25,263
I suggest a 555 one-shot driving a transistor to generate the pulse.

#### Dodgydave

Joined Jun 22, 2012
9,313
A simple capacitor pulse would work, like this...

#### crutschow

Joined Mar 14, 2008
25,263
A simple capacitor pulse would work, like this...
You likely need a much larger capacitor for the 10.5Ω chime solenoid, likely in the neighborhood of a few mF..

On second thought, just a logic-level MOSFET with a capacitor input to the gate and a resistor to ground should work to generate the pulse (below).
That will also keep the (likely small) contacts in the clock mechanism from carrying the large solenoid current.
The MOSFET can be just about any logic-level N-MOSFET with a current rating of 1A or more.

#### RMHC

Joined Nov 13, 2019
45
Hi to Dodgydave & Crutschow,
I am not sure who is responsible so here goes. Many thanks to you both for the comments and circuitry. The clock motor requires 1.5v to operate so the hourly pulse will be 1.5v supplying the circuit you drew. The 6v. is only to operate the chime solenoid, everything else is 1.5v. I am attaching a modified circuit showing what I mean. What is the best way to get 1.5v. from the 6v. battery and how will the circuit be affected by the change? Looking forward to hearing your thoughts on this, thanks again. RMHC.

#### crutschow

Joined Mar 14, 2008
25,263
You clock diagram shows a switch generating the pulse, so I assumed you could connect 6V to that switch.
Is than not the case?

If you can use the clock switch that way, then you also need to add a 1meg resistor at the input to C1 to ground, which I forgot to add..

#### RMHC

Joined Nov 13, 2019
45
You clock diagram shows a switch generating the pulse, so I assumed you could connect 6V to that switch.
Is than not the case?

If you can use the clock switch that way, then you also need to add a 1meg resistor at the input to C1 to ground, which I forgot to add..
Hi, Many thanks for the reply. The hourly trigger pulse is derived by the clock movement by simply connecting the 1.5v. supply for the clock motor to the trigger o/p every hour on the hour. It stays connected for a minute or two until the minute hand releases it as it leaves the 12 position. The 1.5v. for the clock has to be derived from the 6v. battery by whatever is the best way- dropping resistor or zener diode or whatever. The red lines on my last diagram indicate the clock supply with the gap left for the dropping cct.
Because the load on the 1.5v. is increased at the hour when the chime is energised I guess a dropping resistor is a bad idea. As you suggested earlier the clock contacts are very light duty and not designed for more than a few milliamp load. I really appreciate your input on this and look forward to hearing from you again. Hopefully I will be able to get things working
in due time. Thanks again. RMHC.

#### RMHC

Joined Nov 13, 2019
45
Hi, Many thanks for the reply. The hourly trigger pulse is derived by the clock movement by simply connecting the 1.5v. supply for the clock motor to the trigger o/p every hour on the hour. It stays connected for a minute or two until the minute hand releases it as it leaves the 12 position. The 1.5v. for the clock has to be derived from the 6v. battery by whatever is the best way- dropping resistor or zener diode or whatever. The red lines on my last diagram indicate the clock supply with the gap left for the dropping cct.
Because the load on the 1.5v. is increased at the hour when the chime is energised I guess a dropping resistor is a bad idea. As you suggested earlier the clock contacts are very light duty and not designed for more than a few milliamp load. I really appreciate your input on this and look forward to hearing from you again. Hopefully I will be able to get things working
in due time. Thanks again. RMHC.

#### crutschow

Joined Mar 14, 2008
25,263
So can the contacts be connected to 6V or not?

For good efficiency, you could use a micropower series regulator to generate the 1.5V.

#### Dodgydave

Joined Jun 22, 2012
9,313
I wish to make a striking clock using the following- 1. Quartz clock movement (1.5v.) with hourly trigger switch. 2. Solenoid working on 6v. with 10.5 ohm coil which includes a spring loaded plunger to hit the gong. I have a block diagram for reference on the attached files.
I really appreciate any help with the circuit and hope that a member is interested in helping. Many thanks. RMHC.View attachment 191383

Can you not use a 3V supply instead?..

#### RMHC

Joined Nov 13, 2019
45
Hi Crutschow,
I am afraid I gave you some incorrect info. earlier. So here is the accurate scoop, The hourly contacts are separate from the clock motor entirely. They are a tiny set of NO contacts which close on the hour for a very brief instant. I took the movement apart yesterday to verify the layout. The pulse is caused by a pin on the minute wheel pulling one of the contacts further and then releasing it, allowing it to spring back towards the stationary contact and momentarily touching it on the rebound....
So the 2 wires can be incorporated in the circuit as a NO switch with a brief closed condition. The 6v.can be connected to the contacts but as they are tiny the switched current has to be very low. Thanks for the info. on the micro power regulators- as yet I have not found one for 1.5v but am still looking. Cheers RMHC.

#### crutschow

Joined Mar 14, 2008
25,263
The 6v.can be connected to the contacts but as they are tiny the switched current has to be very low.
The peak input current for my circuit would less than a mA, so the contacts should have no problem with that.

Here's the circuit with the simulated clock switch included:
R3 limits the peak contact current due to the charging of the large MOSFET gate capacitance.

#### crutschow

Joined Mar 14, 2008
25,263

#### RMHC

Joined Nov 13, 2019
45
Hi Crutschow,
You were very quick with that cct. Many thanks.
I am looking for a 1.5v micro reg. to connect the clock motor to the 6v. to complete the cct. Do you think any other tweaks are needed after that? RMHC..

#### crutschow

Joined Mar 14, 2008
25,263
I am looking for a 1.5v micro reg. to connect the clock motor to the 6v. to complete the cct.
Did you look at the one I referenced in post #16?
Do you think any other tweaks are needed after that?
None I can think of.

#### RMHC

Joined Nov 13, 2019
45
Brilliant but the TI datasheet quotes 5.5v as max & 6.0v as absolute max. Comments please. RMHC

#### crutschow

Joined Mar 14, 2008
25,263
Brilliant but the TI datasheet quotes 5.5v as max & 6.0v as absolute max.
Oops, neglected to look at that.

Here's one that goes to 12V max input.