Can someone help me understand,


What I'm trying to understand is where is the processing in this "Dual Mos trigger relay"?

What I mean is, which component specifically are the values being changed and held in as one scrolls through the different modes and set different values for times?

I can see 2 Mofet's (D4184) an octoupler (PCB177) and a rectifier (ss34)...a few resistors and an LED.

Please excuse me if it's too much of Newbi question, but this is where I've decided to jump in. If I can understand and duplicate this timer, it will go a long ways in helping what I'm trying to accomplish.

Thank you in advance.


Most probably a µC will sit below the display.

If that board works "stand alone" there must be some electronics hidden inside or under the display.

It might be impossible to reverse-engineer that thing.

It's usually easier to start-over and design something from scratch that does the same thing than to copy an existing design, especially if there are any programmed parts. But it will cost more to build yourself, it will probably end-up bigger, and unless you make your own circuit board it won't be as "elegant".

Thank you.

I really only did need the programmable infinite cycle mode to be integrated into a whole other project, and do eventually (hopefully) plan design the whole thing as one.

Part of what I was trying to accomplish was not duplicate parts from the timer and the mppt charger using cn3722.

I live in the America's, wouldn't that be a reverse to reverse engineer something from the far East :slight_smile:

Link corrected:

OK, that module is based on an ASIC integrated into the display. The concept of "reverse engineering" it is quite meaningless, and given the way these modules are produced, it is most unlikely you could find the timer/ display module itself for sale, let alone anything resembling a datasheet.

You have two choices. Buy the module and plug it into your system ready-to-go, or use an Arduino, add a display module such as are also available on eBay, and whatever other interface components you need and program it to do what you want.

Do the specifications of that module match your requirements? If so it would be pretty pointless not to just buy them. :roll_eyes:

Paul, Thank you.

It does have the features i need, but I hope to produce a marketable product when I'm finished, so my goal was several fold.

  1. learning how that time is constructed will help me in designing my project.

  2. streamline the circuit as to not duplicate parts and save space and money.

  3. Since there is an LCD, it would be nice to use it to get Volts and Amps read out.

While I'm kind of protective about what I'm working on, It is done in the spirit of community and planetary health and well being.

What I am designing is a small footprint solar charger with an infinite cycle timer built in to operate hydroponic systems in areas where it is difficult to grow stuff now.

The timer needs to be programmable for different conditions, but more or less needs to come on 1-2 minuets per hour.

Since I am planning on using the CN722 but unfortunately it does not look like it will handle the timing tasks, so in trying to figure out this timer, I thought I could just integrate the feature I needed.

In looking at a similar timer, it uses the stm8s103f3p6.

May be a place to start I suppose.

Thanks again for the reality check.

This is an Arduino forum, other controllers are discussed in other forums. Do you really want to use different chips for timer, display driver etc., instead of using a single µC?

Please forgive me for not being real clear. I have an Arduino starter kit, I know what I'm trying to accomplish, but not sure on the most efficient way.

I would like to make a small MPPT solar charger. Based on my research so far, the cn3722 seems to be made for that. The reason I'm wanting to make this charger is to use it for remote hydroponic systems.

Therefor, a crucial part of the overall project is the timer, specifically, the infinite cycle mode for a 12v pump.

In inquiring about the technology about the time, I was feeling my way in the dark about a starting point, build the charger around the timer, or the timer around the charger.

The charger schematics are made available by the maker of the chip. I'm (in my head) trying to integrate the timer and charger to share the LCD.

I don't deny probably being out of my league, but never have I failed keeping in mind that the greatest journeys are completed one step at a time, specially with the helping spirit of humanity.

I'm not dead set on using that chip set if there is a better way to achieve the goal (a small, efficient, solar charger with/and? a timer relay.)

I'm not opposed to using the relay I inquired about, just wanting to make sure it's the best way to go.

I will take any criticism with grace and direction with appreciation.


The "Typical Application Circuit" of the CN3722 does not include an LCD display nor timer. It also lacks any interface to a controller. Are you sure that you know what you want to make how?

I'm sure what I want to make. How is what I'm trying to explore and figure out if it's possible.

Will build a " "Typical Application Circuit" for the cn3722 and forgive me if I sound mentally deficient here but hard wire into the circuit a volt and amp meter reading to a common shared LCD with the timer.

Other than that, the charger and timer are independent of one another (with the exception of exploring the function of having the charger kick on the relay automatically when the battery is fully charged).

I would like the charger and timer on a single board for ease of production and final packaging with a battery pack.

While I realize the Nano maybe better suited for what I'm doing, I'm starting with the UNO because that's what I have on hand now.

Please show the circuit diagram you're talking about, with a relay. In the data sheet a MOSFET is used instead of a relay.

Will do when I get it tuned in. That's partly why I found that timer relay appealing, it uses MOFET's and no capacitor which tend to be the weak link in the long run.

I thought it would be easier to borrow from it, but that's where I'm at now, figuring out timer options that can be integrated with cn 3722..

It may just end up being best to use the timer above and the charger separately and not have to design something from the start, but thought it would be cool of it could be done.

In the back of my mind what I was thinking was someone would respond telling me which 2 or three pins on that timer to jumper to a serial connection to be able to get in it's brains. Maybe a little naive, but not unheard of.

I heard a saying once "if you're green, you're ripening, - if you're ripe, you're rotting"

That's my excuse for being green, should I need one that is.

As I don't know about your timer I can't give you any hints, except asking for a data sheet.

The required parts for such a timer module are:

An RTC chip and crystal and backup-cell or supercap (or module including both).
A microcontroller
Buttons (at the very least needed to set the time etc)
Switching component(s), ie relay/MOSFET/opto-triac
and the programming to tie it all together.

The module linked to has microcontroller/RTC/cystal/backup cell all mounted under or as part of the display,
which is why it was hard to fathom. (But this clearly makes sense commercially as that is the guts of a time
switch unit - its likely a masked ROM microcontroller too, saving the expensive programming step during
manufacture - or it could be a hybrid of an RTC and microcontroller in one chip to reduce the BOM)

If you are making an integrated charger and timer then you would need to add components related to charging
(adjustable DC-DC converter and some voltage dividers and current shunts?) and add some more code to the


Thank you for trying. Working backwards, what is the most basic micro controller that can be used with the (555) for timing.

From there, when I look at the most basic Arduino experiment, flashing an LED, that seems to be all I need out of a timer, specify the time on and the time off and instead of an LED, MOSFETs?

I may take the lcd off the timer, after you mentioned it, I looked and there is something hiding under the lcd, but does not seem to be part of or one with the lcd.

It likely is an ASIC design, but I've seen these timers made differently seemingly by different factories that I may be able to find just what I need to build around.

Am I making it this more difficult than it needs to be? Maybe, but I won't know till I try.

While I don't profess to know much about much, I think wiring in a voltmeter to get a read from the solar panel and the battery is very basic and will add a nice and useful feature to the charger

Having a built in timer with a usb port all packaged nicely behind a 10-20W solar panel is something that doe's not currently exist, but is marketable i believe.

I've been working with outdoor hydroponics for a while and dare say I've pioneered techniques that are very efficient, the right combination of charger and timer make it possible to do things that would of been difficult not that long ago.


thanks for not kicking me in the knees. I will definitely take the lcd now and look,. I already fried one and waiting on replacement MOSFETs as the clock seems to still work.

Took one for the team, Maybe. Might be able to put it back together.

SC92F7003X is what's sitting under the the lcd.

Datasheet you want, boom!

4 matching letters are not enough nowadays for a hit :frowning:

I could find a page at, but my Chinese is very limited and the English translation timed out.

I took out the x, and came up with a little more hits.,,SC92F7003

SC92F7003 - Google Search

Looks like it maybe a knock off of STM8S003 or same as.

stm8s003 - Google Search

Looks promising that at least it's not an ASIC deisgn.

found it,

Looks like an 8051, else quite similar to an AVR µC if the code cannot be read out.