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Components and Circuits For discussions about component types, alternatives and availability, circuit configurations and modifications etc. Discussions here should be of a general nature and not about specific sets.

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Old 29th Jun 2022, 4:16 pm   #1
John10b
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Default Run back timer

Not sure if this should be in modern technology?
What is the difference between a normal timer and a run back timer ? Thanks.
John
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Old 29th Jun 2022, 6:12 pm   #2
duncanlowe
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Default Re: Run back timer

Well it kind of hinges on what a 'normal timer' is.

As I understand it a run back timer runs down, a bit like an hourglass and switches off the load if it hasn't been switched off by the user. So it sets a maximum ON time. Used on bathroom heaters these days to make sure it doesn't get left on.

A run on timer is another kind. That means that it keeps an appliance running for a set period after it has been switched off. Typically a bathroom extractor fan.

There are loads of others but hopefully this explains what you wanted?
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Old 29th Jun 2022, 6:53 pm   #3
John10b
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Default Re: Run back timer

Thank for replying. Probably it’s me misunderstanding the terminology. For example if I was told a bathroom heater had a timer I would assume just that, it would run for the set time. So when I saw on our new bathroom heater was fitted with a “ run back” timer I was a little puzzled.
John
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Old 29th Jun 2022, 8:02 pm   #4
broadgage
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Default Re: Run back timer

Time switch=Uses a clock mechanism to close or less commonly open a circuit at certain times each day. Some types can be set for different times on different days.

Run on timer=causes a load to be turned on by manual or automatic means and then to continue running for a set time after the "start" signal is removed.
Example is an extract fan in a bathroom, the turning on of the room light by a manual switch or by an automatic presence detector starts the fan. The fan continues to run for a set time after the light is turned off.

Run back timer=Manual operation of a control closes a circuit and keeps it closed for either for a preset time, or for a time set by the user.
Examples include heaters in a waiting room, press button to turn heaters on, they then remain on for say 20 minutes after which the user may press the button again. Avoids waste, and wont be triggered by animals might be a presence detector.
All modern electric toasters incorporate a run back timer, which is started by inserting the bread and pressing the lever that lowers it. The time is adjustable to suit differing preferences and types of bread.
Microwave ovens similarly.
Older run back timers use a clockwork mechanism and can be heard ticking, modern units use a solid state circuit.

One type is not even electrical, a simple clockwork mechanism that is wound up and started by turning a knob to the desired time interval. When the set time expires, the clockwork rings a built in mechanical bell. Often used to time cooking. The timer does NOT control the cooker, but reminds the cook to turn the cooker off or remove the food.
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Old 29th Jun 2022, 10:21 pm   #5
John10b
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Default Re: Run back timer

Thank you for detailed explanation, I now understand the difference many thanks.
John
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Old 29th Jun 2022, 11:24 pm   #6
Glowing Bits!
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Default Re: Run back timer

I have a plug in run down timer on a wall mounted infrared heater, it turns it off after about 50 mins or so, it's great for keeping the bills down and reduces the risk of a fire should it be left on overnight.
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Old 30th Jun 2022, 9:41 am   #7
60 oldjohn
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Default Re: Run back timer

For anyone making a runback timer or timer should be aware of the new kid on the block. For many years we had the NE555 timer IC with limited time count and used a capacitor for the time delay. Jump forwards 50 years and the C005 is available, times from 2 seconds to nearly 6 weeks. Only needs one resistor and one or two links to set the time and its miniature in size. https://westsideelectronics.com/delay-timer-ic/ The whole circuit is les than half an inch square.

https://www.ebay.co.uk/itm/201538746...wAAOSwwpdW4Rpz I hope this is allowed, there are other sellers, some times these chips are hard to locate on line.

John.
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Last edited by 60 oldjohn; 30th Jun 2022 at 10:10 am.
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