Schematics of delabs

One of the oldest Schematic Archives on the Web. It was in the form of pdf files in the late 90s. Instrumentation and Industrial Designs by delabs and Generic Application Designs.

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Monday, May 18, 2015

Frequency Divider 74HCT4040

U1 7555 is a CMOS version of 555. The 555 here is in Astable Oscillator mode, C1 and C4 are decoupling capacitors 0.1uF value, ceramic disc.

Mixed and Interface Circuits

The output is around 100kHz, If C3 is plastic or mica the frequency output will be stable with temperature. It is better to use a crystal oscillator.
Frequency Divider 74HCT4040

The 555 output is fed to clock input of 4040, the output of 555 will be a square wave, on every high to low transition (falling edge or negative transition) the counter increments by one and the output is 12 bit binary.

Read more at my Digital Timers, Counters and Clocks

If input frequency is F the final output at Q12 is F/4096. The period T = 1/F.
If you make the 555 run at 1Hz, C3 around 7uF, Then this circuit becomes a long duration timer, the Q12 period will be 4096 seconds or 68 minutes.

Wednesday, May 13, 2015

Passive volume control with Potentiometer

Volume control circuit for speaker 4 ohm or 8 ohm located in the another room far away. by using only passive components. This gives limited control and helps reduce volume when a conversation starts. The resistors are very low value.

Passive volume control

Passive volume control with Potentiometer

A simple circuit you can build at home at low cost it uses just a rotary switch and wire wound resistors. Add more resistors and a rotary switch with more contacts for finer control.

More Hobby Ideas and Projects at Hobby DIY Garage

Guitar Speaker

An easy project to start DIY electronics is the Guitar Speaker. Make a good Acoustically friendly Wooden Box. Add a 20 Watt Audio Amplifier and a Large Speaker, There is a Power Supply too in this box. If you hear a Large Hum over the Strumming of the Guitar. You are in Business.

You should know that this is a limited design, it is used when the speaker is far away from audio amplifier. In the early days  audio amps were made of power transistors and signal transistors. (they came after  valves), No remote controls, Radio tuners, Spool Players and Turntables would be connected to these via a Preamplifier and Rotary Switches.

The Speakers in large wooden boxes would be kept at the far corners of the Hall, you could have a passive volume control in this with a Neon flickering indication of audio.  That circuit is here Music Sound to light converter.