Time delay relay for delaying the switching on/off of the receiver - retro presentation - E. Dold &a

p.kaczmarek2 885 3

TL;DR

A transparent E. Dold & Söhne KG “minitimer” time-delay relay delays receiver switching on or off by an adjustable 0.5–10 seconds.
It uses a fully electromechanical mechanism: a mains AC motor and electromagnet engage a pinion, drive gears, and a spring-loaded clockwork countdown.
The front panel shows VDE 0435, 220 V supply terminals A1/A2, and contacts 15, 16, and 18 for NC/NO switching.
The relay visibly counts down, switches the contacts at timeout, and resets when power is removed, while drawing almost 5 watts throughout operation.

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Post #1
21904552 17 May 2026 09:13

Time for a break from the ubiquitous microcontrollers and 'smart' devices. Today we're taking a look inside another retro piece of equipment, this time made by German company E. Dold & Söhne KG. This will be a timer relay that delays the switching on/off of a receiver for an adjustable time between 0.5 and 10 seconds. I will demonstrate its operation here with short videos, show the interior and the principle of operation.

The transparent casing already explains a bit to us. This type of device is fully electromechanical and there is no microcontroller or even a simple NE555-type pulse generator inside. These are not the times, moreover it would be redundant.

The front shows the name 'minitimer', the standard to which it was made (VDE 0435) and the internal schematic. Power is supplied to the A1 and A2 screw terminals, nominally 220 V. On the right we have a knob for adjusting the response time, and in the centre a window where, when the power is off, the currently set time value can be seen. When the equipment is powered up, you can in turn see how much time is left to switch on. In addition, the device has terminals 15, 16 and 18, where 15 is a common contact, 16 is a normally closed contact (NC, opens when time expires) and 18 is a normally closed contact (NO, closes when time expires). Potentially there is still room for pair 21 and 22, but in this version it is not occupied.

The transparent casing immediately reveals the general principle of such equipment. It is vain to look for any electronics here, there is not a single transistor, and the whole thing works mechanically. The time-setting knob drives a spring-loaded clock mechanism via a worm gear. Just how is it that the device can perform multiple cycles without another winding?

We'll check soon - just a video presentation to come:

Side view - synchronous motor:

From the other side - you can see how the drive is switched on, you can see the movement of the NO/NZ contact (normally open/normally closed, possibly normally open/closed):

Let's go back to the question posed - how is it that the device can perform multiple cycles without another screw-up? Let's remove the casing and check.

The video here shows perhaps the most interesting part of the mechanism. Here we have an AC motor that is connected to an electromagnet. When power is applied, it pulls the pinion towards itself, so that the rotary motion is fed further through the gears and the mechanism can 'count down' until the contacts short circuit or open. When power is lost, the pinion moves up again and the spring retracts the mechanism to the setting selected by the user.
Below, the same thing, but with the motor locked (resting against the table):

And without locking:

Gallery:

On the other side you can see the simple gears used just to transfer movement from the motor to the actual timekeeping mechanism. There is nothing overly complicated here - several gears with matched ratios slow down the rotation of the motor to match the desired range of adjustment. Modifying this mechanism allows the manufacturer to easily create different versions of the product differing in the range of possible deceleration.

It remains to do the rest of the disassembly, the motor is connected directly to the power terminals, it is an AC motor, it runs on mains voltage:

Gearboxes and the spring already discussed:

The video shows the mechanism that short-circuits/opens the contacts (pawl on the cog):

Here you can also see the timeout locking pawl:

Finally, you can still see the engine:

Out of curiosity, I also measured the power consumption - almost 5 watts, and this was for the entire duration of the device's operation, including after the countdown timer had expired. Quite a result, especially as a modern "smart socket" with a Wi-Fi module and relay draws less than 1 W....

In summary, this was a gallery from inside an old time relay. It may not have been anything extraordinary, but I personally see a kind of beauty in such all-electromechanical solutions and wanted to share it. What surprised me most was the way the electromagnet releases/engages the gearbox from the motor. Undoubtedly such devices have their own unique charm.
Do you use/have you used this type of relay, how do you rate its failure rate? What applications do you see for a delay of 0.5 - 10 seconds?

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#2 21904585 17 May 2026 10:31

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Post #2
21904585 17 May 2026 10:31

Such relays can still be found and still work today. I used a similar one to extinguish my Beryl 102 when I went to bed. It had different timings, of course, but was incredibly loud. Then I got my hands on a Polish-made automatic staircase machine, which turned out to be even louder. Compared to the device presented here, it was primitive. The time was adjusted by breaking the pins on one of the wheels. It was a one-way adjustment
Until about 10 years ago I heard the familiar sound of this switch in one stairwell. It could have been 50 years old.
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#3 21904778 17 May 2026 14:45

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21904778 17 May 2026 14:45

A similar motor drove the programmers of old washing machines, pure electromechanics with no RC timers not to mention counters.
#4 21905125 17 May 2026 22:17

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21905125 17 May 2026 22:17

The one from washing machines (e.g. PS 663) sat in RTs relays. Too big by today's industry standards, but robust.
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FAQ

TL;DR: This 220 V relay uses an adjustable 0.5–10 s clockwork delay and "not a single transistor" to switch a receiver after power is applied or removed. It suits restorers, relay hobbyists, and technicians who want to understand how a retro E. Dold minitimer works, why it resets automatically, and where such short delays still make sense. [#21904552]

Why it matters: This thread shows how a fully electromechanical timer solved short-delay switching with gears, a spring, a synchronous AC motor, and an electromagnet instead of electronics.

Alternative	Timing method	Noise level	Power draw	Notable point
E. Dold minitimer	Synchronous motor + gearbox + spring	Lower than older stairwell timer	Almost 5 W	Transparent case and contact display
Modern smart socket	Electronic control + relay + Wi‑Fi	Not stated	Less than 1 W	Lower standby power
Old stairwell timer	Mechanical wheel with break-off pins	Very loud	Not stated	One-way time adjustment

Key insight: The clever part is not the clockwork alone. The electromagnet couples the gearbox to the mains-powered motor only while energized, then lets the spring reset the mechanism for the next cycle.

Quick Facts

Front-panel markings and hardware identify a VDE 0435 timer relay with A1/A2 supply terminals, nominal 220 V input, and a delay range adjustable from 0.5 to 10 seconds. [#21904552]
The output uses 15 as common, 16 as NC, and 18 as NO; when time expires, 16 opens and 18 closes. [#21904552]
The transparent window serves two roles: with power off it shows the set delay, and with power on it shows the remaining time until switching. [#21904552]
Internal construction is fully electromechanical: a worm gear sets spring tension, simple reduction gears slow the motor, and no transistor or NE555-style timing circuit is present. [#21904552]
Measured operating consumption is almost 5 W for the whole energized period, including after timeout, versus less than 1 W for a modern Wi‑Fi smart socket mentioned for comparison. [#21904552]

How does the E. Dold & Söhne KG minitimer delay relay work without any electronics or microcontroller inside?

It delays switching with a spring-loaded clockwork mechanism driven through gears by a mains AC motor. The knob preloads the mechanism through a worm gear, then the motor advances it until the contact set changes state at the selected point between 0.5 and 10 seconds. When power is removed, the mechanism returns to the preset position for another cycle. [#21904552]

What is a synchronous motor in a retro time delay relay, and why was it used in devices like this E. Dold minitimer?

A synchronous motor is the mains-powered drive that turns at a speed tied to AC frequency, giving stable motion for the timer gear train. "Synchronous motor" is an AC motor that runs in step with the supply frequency, giving predictable rotational speed for timing mechanisms. In this relay it directly drives the reduction gears, so the designer gets repeatable short delays without transistors, RC timing parts, or counters. [#21904552]

What does the VDE 0435 marking mean on an old timer relay, and what does it say about the device?

It shows the relay was built to the VDE 0435 standard named on the front panel. In this thread, the marking mainly tells you the unit is a formal, standards-marked industrial product rather than an improvised timer. The front also prints the internal schematic, which helps identify the contact logic and supply terminals before testing. [#21904552]

How are the A1, A2, 15, 16, and 18 terminals used on this 220 V E. Dold time delay relay?

A1 and A2 take the 220 V supply, while 15, 16, and 18 are the switching contacts. Terminal 15 is the common contact, 16 is NC, and 18 is NO. After the selected delay expires, 16 opens and 18 closes. The housing also leaves space for another pair, 21 and 22, but this version does not populate it. [#21904552]

Why does the electromagnet in this electromechanical timer engage and disengage the gearbox from the AC motor?

It couples the motor to the timing train only while the relay is energized. When power is applied, the electromagnet pulls the pinion into mesh so the motor can drive the gears and count down. When power is lost, the pinion moves back up and the spring resets the mechanism to the user-set position. That design enables repeated cycles without rewinding by hand. [#21904552]

How do you adjust the delay time on a mechanical relay with a spring-driven clockwork mechanism and worm gear?

You turn the front knob, which drives the spring-loaded timing mechanism through a worm gear. That changes the starting position and stored spring force, setting a delay anywhere from 0.5 to 10 seconds. With power off, the center window shows the chosen value. With power on, the same window shows how much time remains before the contact change. [#21904552]

What causes an old electromechanical time relay to keep drawing nearly 5 W even after the countdown has finished?

It keeps consuming power because the mains AC motor stays connected to the supply during the entire energized period. The thread states the motor is connected directly to the power terminals and runs on mains voltage. A measured reading showed almost 5 W not only during the countdown, but also after timeout. That makes it far less efficient than a modern smart socket drawing under 1 W. [#21904552]

Where can a 0.5 to 10 second delay relay be useful in practice, especially for delayed switching on or off of a receiver?

It suits short on-delay or off-delay tasks where a few seconds matter and long timing is unnecessary. The thread specifically describes delaying the switching on or off of a receiver, and one commenter used a similar relay to switch off a Beryl 102 at bedtime. A 0.5 to 10 second range also fits simple sequencing where contacts must change after a brief pause rather than instantly. [#21904552]

How reliable are old electromechanical delay relays like the E. Dold minitimer compared with modern electronic timer relays?

They can be remarkably durable, but they trade efficiency and silence for mechanical longevity. One commenter says such relays can still be found and still work today, and recalls hearing a similar stairwell timer in service until about 10 years ago that could have been 50 years old. Modern electronic timers use less power, yet the thread presents these older units as long-lived and still functional. [#21904585]

What are the most common failure points in vintage timer relays with gears, springs, pawls, and mains-powered synchronous motors?

The weak points are the moving parts that must stay aligned and free to move. In this design, the likely trouble spots are the gear train, the return spring, the electromagnet-shifted pinion, the pawl that changes contact state, and the contact set itself. If any of those binds or fails to latch, the relay may stop counting down, fail to reset, or miss the NO/NC changeover. [#21904552]

How does an electromechanical delay relay compare with a modern smart socket or NE555-based timer for short delays?

The electromechanical relay is bulkier, fully mechanical, and much less energy-efficient, but it works without any transistor or pulse IC. The thread contrasts it with both modern smart devices and an NE555-style generator, noting that this older unit has neither. Its measured draw is almost 5 W, while a modern Wi‑Fi smart socket with relay draws less than 1 W. [#21904552]

Why were old stairwell timers and washing machine programmers often much noisier than relays like the E. Dold unit?

They were louder because their mechanisms were simpler, more exposed, or coarser in operation. One commenter describes a Polish automatic stairwell timer as even louder than a similar relay and says its time was adjusted by breaking pins on a wheel. Another notes that old washing-machine programmers used a similar motor, meaning they also relied on continuously moving electromechanics rather than quiet electronic timing. [#21904585]

What is a timeout locking pawl in a mechanical timer, and how does it control the relay contacts?

It is the latch that holds or releases the mechanism when the set time expires, forcing the contact assembly to change state. "Timeout locking pawl" is a mechanical latch that catches part of the timing train at the end of travel, defining the timeout point and triggering the relay’s NO/NC contact movement. The thread shows it near the cog and also shows the pawl that opens or closes the contacts. [#21904552]

How can you safely inspect, disassemble, and test a 220 V mains-powered retro time delay relay?

Start with the assumption that the motor and supply terminals carry full mains voltage at 220 V. 1. Inspect the printed schematic, terminal markings, and transparent case before opening it. 2. Disconnect power, remove the cover, and check the gears, spring, and contact movement by hand. 3. Re-energize only with insulated connections and clear access, because the motor is directly connected to the power terminals. [#21904552]

What should you check when restoring an old E. Dold or similar timer relay that no longer counts down or switches the contacts properly?

Check whether the motor turns, the electromagnet pulls the pinion into mesh, and the spring resets the mechanism after power loss. Then inspect the simple reduction gears, the timeout locking pawl, and the NO/NC contact movement for sticking or incomplete travel. If the motor runs but timing fails, the fault is likely in the coupling, pawl, or gear train rather than in electronics, because this relay has none. [#21904552]