Vermes
Advanced Member level 4
It is a device for starting internal combustion modeling engines. The device is portable, so you do not have to carry the modeling box when refueling and restarting the model. There is a possibility of simultaneous connection and operation of the starter and the system for heating up the glow plug. The device uses converter inverted step-down. All is closed in a metal housing T-65. Accumulator 12V/7,5Ah. On the front board there is a 12V backlit switch, twisted lab clamps, ammeter with a range of 5A, 1k linear potentiometer. On the upper board there are clamps for starter. Front and upper boards were designed in Designer, using color self-adhesive paper, covered with glue for repositioning and foil with print in mirror.
Pictures:
Schematic and printing and components system:
Transistor IRFZ46, Schottky rectifying diode MBR750. After substituting the following data: f=52KHz, Uin=12,6V, Uout=1,6V, I=5A, program calculated inductance of the choke to 20uH. The choke was made of a yello-white core of old ATX power supply. It had 23 windings winded simultaneously with 3 wires DNE0,5. At a frequency of 50kHz the penetration depth of the current is 0,3mm, so the maximum thickness of the wire is 0,6mm. Measure resistor was made of two metalized resistors 0,1ohm/2W, connected in parallel. Power produced by those resistors is about 1,5W at maximum efficiency.
Power consumption from the accumulator is about 1,5A at output efficiency of the power supply – 5A. Transistor of the converter does not heat up at all, but anyway it was equipped with a small heat sink. Diode MBR750 with the heat sink heated up to 60-80 degrees Celsius after 2 minutes of operation at maximum efficiency, the choke was slightly warm, but in practice you do not heat up the glow plug for so long.
Pictures of waveforms:
- from the output clamps
- from the 3 pin (current sense) of the UC 3843 system
Link to original thread (useful attachment) - Zasilacz do uruchamiania silników modelarskich
