domingo, 17 de abril de 2016

Toaster Controller A0201D

1. Description
I found few days ago a toaster on a street. I normally do not pick this type of gadgets because I feel that somebody else may use them for better - but this time I got the electronics.

Because I only got the control board, I do not know the model: it was a toaster for two-slices, with independent selectors and three operation buttons: "reheat", "cancel" and "defrost".

For each slice-heater there is a control, with two boards each: for the timer/controller and for the buttons. 

Pictures of the control board and buttons:



The boards are 80*50 mm and 105*20 mm.

They are connected by 5 cables, and they have the following marks:
KT-223-MAIN for the main board,
KT-223-KR or KT-223-KL for the button boards (right & left).

The main board has two additional connector sockets: one with two pins, which is for the relay activating the heating AC side, one with three pins, which is the DC power supply for the board.

2. ICs for Toasters
The IC at the core of this board is labelled as:

I have not managed to get the datasheet of the IC A0201D - this is probably related to an intelectual property issue, at least this is what I asume.

This youtube upload is titled A0201D, and clearly talks about a toaster (model Aurora AU 153). It also mentions IC PT8A2511. Unfortunately it's ... in Russian!

This other webpage has the European certificates and tests on a toaster. The certificate mentions two suppliers for the control board, and the use of A0201D for certain models from one manufacturer, and PT8A2511 for the same models made by the other manufacturer.

Here, somebody asks for the equivalent subtitute of the A021D IC on a Kenwood TTP112 toaster (no reply was provided). Here some German guys were fighting with another toaster using this same IC (in German!). And there are also some Hungarians having fun/troubles with the toaster and the IC, and quoting pages in Chinese!

(In this Babel Tower I'm only missing the Finns!)

The A0201D chip is not unheard of: it is possible to find it on sales pages ( here or here), but no way to find the datasheet...

At least, for what seems to be an alternative IC, the PT8A2511, a datasheet is readily available (see here). As per the Hungarian blog mentioned above: "The Russians dare to believe and 99.99% certainty that the IC is the same as the PT8A2511".

In this page, which may be a/the manufacturer of the A0201D, the supply voltage is mentioned to be 3.5-5.5 V (other sources mention 12 V for the control board of toasters).

So, all in all, I have managed to collect the following:

- The "EMC Emission Test Report" for an electric toaster in whose control board, for some models, is installed the A0201D IC, as well as the PT8A2511. (The document is skimmed of what is no relevant here). The following scheme is of special interest:

- The PT8A2511 IC datasheet. This is a "CMOS LSI chip designed for toaster", presented in DIP8 package and working at 3.5-4.5 V. It includes few more information besides this scheme:
- The GA5210PH IC datasheet. This is also a DIP8 IC for toasters. The document is mostly in Chinese, mentions a standard range of 9-12 V, and includes the following scheme (among others):

Despite the apparent differences, all schematics share the pin utilization of the IC:
PIN 5 : RX
PIN 6 : OSC / RC
PIN 7 : CX

As per the PT8A2511 datasheet, the PIN operation is as follows:

3. Schematics

The circuit is modeled in QUCS, and can be found here.
A snapshot of the schematics:

1. The IC A0201D is not a sub-circuit, it's only a "box" without functionality. On this regard the schematics is "useless".
2. The lights at the button board are not LEDs (or at least their resistance is equal in both directions...)
3. The power supply (6 V) is just a figure: as mentioned above, I'm not sure of the required voltage.
4. The switches at the button board are actually of the push-button type (momentary, they remain open unless they are kept pushed).

4. Operation
The board is powered from connections S3_3 (VCC) and S3_1 (GND).
The coil is powered through S2_2, but only activated if the transistor T1 is closed, whose base is controlled by  PIN3.
Pushing puttons DR1 or DR2 closes the circuit through ground to PIN1 (a negative pulse). Similarly, pushing puttons RR1 or RR2 closes the ciruit through ground to PIN2. These negative pulses, according to the previous table, activates the DEFROST or REHEAT timing, resp. Once the function is activated, PIN3 activates the AC relay.
Once PIN1 or PIN2 are activated, they generate a positive voltage which keeps on the lights in the button board (DEF and REH).
If the main board is powered, the POW light is on through the direct VCC-GND circuit, regardless of the position of CR1/CR2.
If CR1 or CR2 are closed, in addition, a branch is closed through the base of the transistor Q1. Whether the voltage at the base is enough to overcome the transistor resistance will depend on specific values, but if it can, then it will also activate the coil which controls the heating of the slices.
VCC to PIN4 is constant.
The variable resistors VR1&2 control voltage at PIN6, and then the frequency of the oscillating system and the duration of the pulses at PIN2 and PIN3.
PIN5 and PIN7 are likely starters for the time counter controlled by the oscillator.

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