Solid State Relay – Common

 Mains-Power, Solid-State-Relay  No Responses »
Oct 282004
 
Solid State Relay - Common

This is a DC controlled Solid State Relay which can turn 230V AC equipment on and off. The output is like a NO normally open contacts of a relay and have to be in series with the Load like any other switch. This should not be used for large inductive loads like big motors. The Q1 transistor limits the current thru the LED by providing an alternate path for more current. The DC input can be from 3V to 20V. The Triac can be chosen depending on current in the load. Look for datasheets and applications at STMicroelectronics for BTA41600 Read More …

 Posted by admin at 7:38 PM  Tagged with:

Battery Backup Supply

 Embedded-Systems, Power-Supplies  1 Response »
Oct 282004
 
Battery Backup Supply

This is a 9V power supply which will work even on power failure. It uses a rechargeable battery and regulators. A transformer with 15-0-15 AC volts output is required. In the first regulator U1 the output is lifted up by 1.4V and in the second regulator U2 by a resistor divider. In the second regulator the voltage across resistor R3 is 5V, so the current is 5V / 1K = 5mA this adds to the quiescent current of 5mA from the regulators ground terminal and flows into the resistors R1 and R2 in parallel which form 404 ohms, 10mA thru Read More …

 Posted by admin at 7:37 PM  Tagged with:

Isolated dual power supply from 5V

 Discrete-Circuits, Power-Supplies  No Responses »
Oct 272004
 
Isolated dual power supply from 5V

This is a unregulated supply for low power circuits. You may be able to regulate the outputs with zeners or small regulators like 78L05. The transformer can be hand wound in a mini ferrite pot core. you can use 2N2222 or any other fast transistor. The transformer should have 1KV isolation. The dot polarity of TR1 should be properly observed, else it may fail to oscillate or give output. Diode should be fast recovery type, for less than 100mA use 1N4148. transformer, pri-20-20, sec-60-60, a SWG-AWG to suit the current you design for, any fast switching transistor would work, no Read More …

 Posted by admin at 10:01 PM  Tagged with:

Music Sound to light converter

 Discrete-Circuits  No Responses »
Oct 262004
 
Music Sound to light converter

This was made by me when i was a kid, it was even published in a magazine, i think it will work, it was used on a very old huge ornamental valve philips stereo system in the remote speakers. Recently i captured this circuit in eagle to publish online, it seems to have a small design error. It worked well for many years. The step-down transformer is used as a step-up here. The secondary winding was around 50mA so the resistance was protecting the 2N2222. (SL100 was used in the original one). C1 and R3 may need tweaking to get Read More …

 Posted by admin at 10:22 AM

Simple Water operated relay

 Discrete-Circuits  No Responses »
Oct 262004
 
Simple Water operated relay

This was done in my early days, i have upgraded it, it ought to work, reduce the number of transistors to make it less sensitive, also a lower value in place of 10M will reduce its sensitivity, use clamping diodes to protect. BD139 is used to drive the relay as it has good Ic. So you can even use a low ohm relay. If a Relay resistance is high its quality is higher, its power consumption is less and it needs thinner wire SWG-AWG. T2 and T3 form a darlington pair which drives T1. LED1 shows that the water level Read More …

 Posted by admin at 10:21 AM

Triac based Lamp Dimmer power control

 Mains-Power  1 Response »
Oct 262004
 
Triac based Lamp Dimmer power control

This is a phase angle control of a Triac which is a evolution from an SCR. The 50 Hz or 60 Hz Sine wave of mains can be turned on at any point after the Zero Crossing The Voltage ramps up in the sine wave which gives a near “Linear” slope which can be used to trigger the ON at a time delay after zero crossing when the voltage is zero. This is like a PWM but works on low frequency only. Some of the early SMPS(HV for TV and Mains Inverter) by Siemens were built around SCRs. Turning off Read More …

 Posted by admin at 8:34 AM  Tagged with:

Telephone status indicator with LED

 Discrete-Circuits, LED-Circuits  No Responses »
Oct 262004
 
Telephone status indicator with LED

This will monitor telephone status without loading the telephone line, this way if you have two phones in parallel you will know if one of them is busy. Connect the two ends of circuit in parallel to phone lines. D1 to D4 make a bridge so that LED’s are powered in correct polarity. LED1 indicates line ok no broken line, LED3 can light only when a 12V Zener breaksdown, this shows if line is busy or free, so that you dont go online when someone is talking on the phone in another room. LED2 lights on an incoming call ringing Read More …

 Posted by admin at 8:31 AM
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