120v AC timer switch for UVC sterilizer boxes to be donated to hospitals

Thread Starter

bennu_500

Joined Apr 7, 2020
3
Hello, I need some help designing a circuit that can activate 1-2 36watt UVC bulbs. I am trying to make a UVC sterilizer box that is as robust, easy to use, safe and inexpensive as possible while being easy to manufacture. I have been researching online for a long time and most circuits I have found require a DC voltage to power the timer and activate the relay. But I recently stumbled across what is called in Europe a "lag switch". It looks very simplistic and appears to run without a common. I am looking for help adapting to a 120v version. I don't care about the slave switch options. Having a ready (power, but not running) LED and a Running LED with a beep/buzzer when done would be nice, but not essential.

Here is a link to the switch I referenced.
https://in.rsdelivers.com/product/cp-electronics/kh1/push-button-timer-light-switch-10-s-20-min/0490194
1586272081307.png
I imagine having any board manufactured with spade connectors for quick build outs for the inputs and outputs. If you feel there are better (or safer) options I am all ears. I intend to use limit switches to ensure the enclosure is fully closed to avoid exposure to the operator.

I would love any input you can provide and if someone was willing to work with me 1-on-1 to help generate eagle files and walk me through getting a board manufactured I would really appreciate it. I am researching and ramping up on a complete design for quick manufacture of the enclosure.
 

Bernard

Joined Aug 7, 2008
5,468
Something to look at; 12 hr. Mechanical Count Down Timer, Cat # TMR-14, All Electronics.
Also Electronic Goldmine.
 

Thread Starter

bennu_500

Joined Apr 7, 2020
3
Something to look at; 12 hr. Mechanical Count Down Timer, Cat # TMR-14, All Electronics.
Also Electronic Goldmine.
Thank you for taking time to look into that for me. I forgot to mention that the timer needs to run for only 60 seconds. Trying to set a 12hr. timer for that short a period of time would probably be very inconsistent if the timer was even able to start with being turned that little.

I did find a timer like the one linked below. But felt it would be hard to put it somewhere in the enclosure where it was easily accessed and not take up part of the main cavity to put items being disinfected.
https://www.amazon.com/dp/B000B8YKF2/ref=cm_sw_em_r_mt_dp_U_zTNDEbE96N3DX
 

Thread Starter

bennu_500

Joined Apr 7, 2020
3
Do you have anything like these available where you are?
https://www.sparkydirect.com.au/p/4679392/clipsal-pneumatic-time-delay-switch-250v-10amp-319-white.html
These are adjustable from 30 seconds to 20 mins.
No electronics involved.
Very interesting. I did not originally look into those as when I saw the name I suspected it required an air source or supplied pressure. They have a fair amount of stuff behind the button. I was hoping to keep the button very shallow so I could place in the front and not intrude into the main cavity. But looks like some of these are more compact than others. I will check into this a little further. Thanks for the lead!
 

AnalogKid

Joined Aug 1, 2013
8,377
Your question has no details about the timing requirements. Repeating cycle / single period; on time range; off time range; adjustment method; size / shape / bulb type; connector method for bulbs; starter required ...

etc.

ak
 

Bernard

Joined Aug 7, 2008
5,468
Best that I could find is 5 min. from Granger, Intermat 6X545, Spring wound timer, @ $ 31.75.
Maybe cheaper on web.
Maybe someone could suggest how to cheaply drop 120 V AC to 5 V DC to control a 1 min. timer
operating a SS relay when lid is opened & then closed ??
 
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Phil-S

Joined Dec 4, 2015
141
Try looking at some of the industrial timers for example Omron H3DT-A1.
They often have very wide supply voltages.
This one does 24 to 240-volts AC or DC
 

Alec_t

Joined Sep 17, 2013
11,141
They have a fair amount of stuff behind the button. I was hoping to keep the button very shallow so I could place in the front and not intrude into the main cavity.
Since transformerless power supplies are a banned topic on this site, any circuit suggested here would have to include a transformer and hence be potentially bulky and inconvenient to build into the sterilizer box. Can't you use a timer which is a self-contained unit into which your box plugs?
 

Reloadron

Joined Jan 15, 2015
5,356
It sounds like all you want/need is a 120 VAC one shot timer capable of 60 seconds. Your load is only two 36 watt (likely UV Germicidal) lamps Place whatever in box, use a micro switch lever actuated on the lid of if safety is a concern use two in series similar to how a microwave over door works with multiple safety interlocks. What's your price point? There are dozens of One Shot timer combinations out there to choose from. Cheap off the boat from China or better quality from companies like Macromatic. Timers like this include a relay so a simple push button switch starts the timing cycle but only if a safety permissive interlock is met. Opening the box prematurely immediately shuts off the lamps and the timing cycle can't be initiated until the box is closed.

This is just a matter of how much quality you want so back to price point. There are dozens of 120 VAC timers out there. Decide on a mounting too?

Ron
 

RobNevada

Joined Jul 29, 2019
54
You could use an ac motor with a gearbox and a cam on the shaft to hit a microswitch. A pushbutton to start and the microswitch to turn off.
 

Janis59

Joined Aug 21, 2017
1,148
1) I would vote for CD4060 actuating the triac or just the high-voltage igbt.

2) RE:""two 36 watt (likely UV Germicidal) lamps"" - Germicidal/bactercidal lamps and viracidal lamps are two very far different things. First are using liminiphore creating about 300-320 nm wavelength killing the bacterias but NOT viruses. For viruses You need luminiphore-less lamps on basis of Hg creating the 254 nm, as well the low pressure or high pessure, and power must be hardly higher. There are plethora of publications reccomending 4 W/m2 for case of CoViD. What is clearly killing the people in short exposition. Thus the personell must keep out whilst disinfection goes on. One minute of 4 W/m2 gives 3,5 zeroes slaughtering a virus. Means between 1000x to 10 000x.
 
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Reloadron

Joined Jan 15, 2015
5,356
1) I would vote for CD4060 actuating the triac or just the high-voltage igbt.

2) RE:""two 36 watt (likely UV Germicidal) lamps"" - Germicidal/bactercidal lamps and viracidal lamps are two very far different things. First are using liminiphore creating about 300-320 nm wavelength killing the bacterias but NOT viruses. For viruses You need luminiphore-less lamps on basis of Hg creating the 254 nm, as well the low pressure or high pessure, and power must be hardly higher. There are plethora of publications reccomending 4 W/m2 for case of CoViD. What is clearly killing the people in short exposition. Thus the personell must keep out whilst disinfection goes on. One minute of 4 W/m2 gives 3,5 zeroes slaughtering a virus. Means between 1000x to 10 000x.
OK, bottom line is two 36 watt lamps so a load below 100 watts. Does that work for you?

Ron
 
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