My first circuit. - Page 1
Forum section: electronics / beginners

author: moontide
author_rank: Contributor
timestamp: January 24, 2019, 11:41:55 am
content: I was trying to make an ocillator..... damn, I forgot the load but I was with an analog oscilloscope.

author: moontide
author_rank: Contributor
timestamp: January 24, 2019, 12:04:33 pm
content: I think there is an interesting startup, but but not going what I wanted.

author: Zero999
author_rank: Super Contributor
timestamp: January 24, 2019, 12:20:14 pm
content: What's the pin-out for the transistor? Is it viewed from the front or back? Please use the proper symbols in schematics, in future.The circuit doesn't look like it'll work.

author: moontide
author_rank: Contributor
timestamp: January 24, 2019, 12:24:12 pm
content: Well, you should have been able to get it.... I'll check

author: moontide
author_rank: Contributor
timestamp: January 24, 2019, 12:27:02 pm
content: Meep

author: moontide
author_rank: Contributor
timestamp: January 24, 2019, 12:30:39 pm
content: I don't understand the circuit but I'm still learning....Ps random time I hit this site and 200+ users and 1800+ guests... lol.

author: Zero999
author_rank: Super Contributor
timestamp: January 24, 2019, 12:50:35 pm
content: It's still not clear, even with the data sheet. Is this the circuit?What's the supply voltage?Where did you get the circuit from?Nothing will happen, the transistor will just smoke, unless the supply limits the current to a safe level.

author: moontide
author_rank: Contributor
timestamp: January 24, 2019, 01:14:12 pm
content: Ok. As far as what I can tell I'm trying to oscillate.I was trying to go:Passthrough charged.Leakage on that.. ramped up to allow proper transister usage.Depletion of that to restart.....Like I said, first circuit.

author: moontide
author_rank: Contributor
timestamp: January 24, 2019, 01:29:25 pm
content: That is a new way of looking at it for me. I got the circuit from my brain. The power supply should be considered variable.

author: Zero999
author_rank: Super Contributor
timestamp: January 24, 2019, 01:41:19 pm
content: Quote from: moontide on January 24, 2019, 01:14:12 pmThat makes no sense. When the circuit is turned on, Q1 will turn on, as current passes through L1. The collector current will depend on its Hfe. The current will keep increasing, as the field builds in L1. The final steady state collector current will depend on: the power supply's internal resistance or Q1's Hfe and L1's internal resistance. If the power supply doesn't limit the current, to a safe level, Q1 will just burn up.The circuit has no way to go back to its original state. To make an oscillator, the circuit needs to be able to flip between two states.

author: moontide
author_rank: Contributor
timestamp: January 24, 2019, 10:14:37 pm
content: So I hooked it up and there did seem to be an ocillation. Around 10 cycles in decreasing amplitude that repeated. There was also another background pattern. After testing multiple points the patterns remained the same. I was perplexed. Then I tested the power supply as I also realised I had no load..... I damaged the power supply and now it is delivering an oscillated voltage....I take this as a win! Lol.

author: Zero999
author_rank: Super Contributor
timestamp: January 25, 2019, 09:33:10 am
content: Where are you measuring the output?It's not surprising there's some oscillation with an exponential decay, as you have an LRC circuit. The inductor has a parasitic capacitance, which will resonate with the inductance and energy will be lost in the resistance of the windings, hence the decay.https://en.wikipedia.org/wiki/RLC_circuitTo make an oscillator, an amplifier is required to cancel out the losses, so the circuit becomes unstamped and oscillates continuously. I'd recommend trying a Colpitts oscillator, as it's very easy to build.https://www.electrical4u.com/colpitts-oscillator/https://en.wikipedia.org/wiki/Colpitts_oscillator