gca08-en
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+ | ====== GCA08 High efficiency universal power supply for 1 or 3 Amp ====== | ||
+ | |||
+ | [[english|{{ | ||
+ | |||
+ | [[english|Content]] -> [[hardware-en|Hardware]] -> [[hardware-en# | ||
+ | * [[mgv-overview-en|The GCA modules]] | ||
+ | |||
+ | \\ | ||
+ | |||
+ | ^^^^By Peter Giling ^^^^ | ||
+ | |||
+ | ===== Description ===== | ||
+ | On many places under the railroad table, we need all kind of DC power supplies.\\ | ||
+ | Buying adapters is one option, nowadays also many of them are high efficiency, meaning not evaporating a lot of energy into heat.\\ | ||
+ | Unfortunately many of these adaptors do not give what they promise.\\ | ||
+ | Furthermore, | ||
+ | And exactly that, specially where infants like to help there parents with this nice hobby, is not much to encourage.\\ | ||
+ | The better option is to run a low 16V ac line under the table and use that.\\ | ||
+ | This power supply will give you that option and can be set-up in various ways and voltages, either adjustable or solid.\\ | ||
+ | For ac input, it needs at least the same voltage as the desired output.\\ | ||
+ | If you are running dc line under the table, it should be at least 2 Volts higher than output.\\ | ||
+ | Adjustable versions could be as low as 1,25 V, up to the maximum you put in.\\ | ||
+ | The switching regulator is very energy efficient. \\ | ||
+ | On average the efficiency will be more than 80%.\\ | ||
+ | |||
+ | There are two units available: | ||
+ | * GCA08-1 1 Amp output, size 40x22 mm | ||
+ | * GCA08-3 3 Amp output, size 40x62 mm | ||
+ | |||
+ | ===== The final results ===== | ||
+ | | {{: | ||
+ | | GCA08-3 the 3 Amp unit | GCA08-1 the 1 Amp unit | | ||
+ | | For both units a professional board is available | ||
+ | \\ | ||
+ | |||
+ | \\ | ||
+ | |||
+ | |||
+ | ===== GCA08-1, | ||
+ | {{ : | ||
+ | This simple supply can be used in different ways.\\ | ||
+ | If you install a standard LM78xx regulator, it can supply a full 1 Amp when the regulator is cooled sufficiently.\\ | ||
+ | Without cooling, it is very depending on the incoming voltage and the used current, how far you can.\\ | ||
+ | If it goes too far (regulater gets too hot) the regulator will stop.\\ | ||
+ | Output voltage can be between 3,3 and 24 volt\\ | ||
+ | This is the cheapest way.\\ | ||
+ | If you use a R-78Ex.x regulator, no cooling is required, and the full load is available.\\\\ | ||
+ | No external settings are needed, since this very efficient chip is option in most common fixed voltages.\\ | ||
+ | The maximum output is 0.5 or 1 Amp, input from transformer can be up to 20V ac or 24V dc.\\ | ||
+ | A total of 6 parts are located on this board.\\ | ||
+ | Efficiency with this power chip is better than 90% which makes cooling totally unnecessary.\\ | ||
+ | \\ | ||
+ | |||
+ | ===== GCA08-3, | ||
+ | {{ : | ||
+ | This board is able to supply 3 Amp in a chosen voltage.\\ | ||
+ | Please refer to tables below for selection of the right output.\\ | ||
+ | \\ | ||
+ | \\ | ||
+ | \\ | ||
+ | \\ | ||
+ | ===== Hardware ===== | ||
+ | | {{: | ||
+ | | {{: | ||
+ | | {{: | ||
+ | | {{: | ||
+ | ^ N.B. Only complete ordered kits will be supported! ^ | ||
+ | \\ | ||
+ | |||
+ | ===== Selecting the output. ===== | ||
+ | This board can be equipped in 1 Amp output max, or 3 Amp, depending on the chosen chip.\\ | ||
+ | Maximum input ratings for all configurations: | ||
+ | dc 30 Volt\\ | ||
+ | ac 24 Volt\\ | ||
+ | For correct calculation of needed transformer, | ||
+ | |||
+ | ^ Selection table for various voltages and current. | ||
+ | |||
+ | ^ Output (V) ^ VR1 for 1 Amp ^ VR1 for 3 Amp ^ R1 ^ R2 ^ P1 ^ | ||
+ | | 1,24 | LM2575T-adj | ||
+ | | 3,3 | LM2575T-3, | ||
+ | | 5 | LM2575T-5 | ||
+ | | 12 | LM2575T-12 | ||
+ | | ||
+ | |||
+ | //** * *short means to insert a short bridge (piece of wire). | ||
+ | **// | ||
+ | |||
+ | |||
+ | ^ Other voltages can be achieved by installing resistor R1 and a small adjust potmeter 20K.^^^^^^ | ||
+ | |||
+ | |||
+ | ^ Output (V) ^ VR1 for 1 Amp ^ VR1 for 3 Amp ^ R1 ^ R2 ^ P1 ^ | ||
+ | | 1,24-12 V | LM2575T-adj | ||
+ | \\ | ||
+ | With this setup output will be adjustable from 1,24 V to max 26 V depending on input voltage.\\ | ||
+ | \\ | ||
+ | Using a potmeter inserts the risk of output changing after a while.\\ | ||
+ | Potmeters are never stable on the long run.\\ | ||
+ | |||
+ | ^ This table shows various , not adjustable voltages. | ||
+ | ^ Vout (V) ^ VR1 for 1 Amp ^ VR1 for 3 Amp ^ R1 ^ R2 ^ P1 ^ | ||
+ | | 6 | LM2575T-adj | ||
+ | | 8 | LM2575T-3, | ||
+ | | 9 | LM2575T-3, | ||
+ | | 10 | LM2575T-5 | ||
+ | | 16 | LM2575T-12 | ||
+ | |||
+ | Vales in this table are a close approach.\\ | ||
+ | Far more exact values can be achieved by using 1% metal resistor from 96 series.\\ | ||
+ | |||
+ | Resistors are calculated by the following formula.\\ | ||
+ | |||
+ | ^R2 = R1 x ( ( Vout/1,24) -1) Ω^ | ||
+ | |||
+ | | N.B. Potmeter is not installed. | ||
+ | |||
+ | |||
+ | ===== Fuse F1 ===== | ||
+ | **ALWAYS INSTALL FUSE !!!!!!!!!!!**\\ | ||
+ | \\ | ||
+ | |||
+ | Do not think it will be unnecessary, | ||
+ | With PTC fuse assembled, you are always safe, and never have to worry about ever having to replace it.\\ | ||
+ | |||
+ | Also the fuse need to be adapted to the the desired output.\\ | ||
+ | In general the values for the multifuse should be:\\ | ||
+ | For 1 Amp out use 0,5 - 0,8 Amp fuse.\\ | ||
+ | For 3 Amp out use 1,5 - 1,85 Amp fuse.\\ | ||
+ | \\ | ||
+ | ===== Which transformer ? ===== | ||
+ | Basically the transformer should have the following parameters: | ||
+ | Secondary voltage : minimal equal to output.\\ | ||
+ | Power (in VA) Minimal (V x A x 1.2), where :\\ | ||
+ | * V = Volt output \\ | ||
+ | * A = Ampere output.\\ | ||
+ | |||
+ | It is possible to use a DC power supply.\\ | ||
+ | The input voltage should be at least 3V higher than output.\\ | ||
+ | |||
+ | |||