#Diptrace v1.20 how to

#Diptrace v1.20 how to

But to be clear, is the objective to use the OSH Park board you ordered as the cycling circuit.and then the question is how to buffer the board output for a one-off higher power version? So the idea of separating the circuit into the cycling/alternating portion from the buffering portion (to drive the 1 Amp bulbs) is a good one. If you only have 12V DC to start with, going thru a 100K resistor can supply at most 12V/100K = 0.12 mA which is woefully inadequate if you want that transistor switching 1 Amp. In addition to charging the capacitor for the cycling function, this resistor must also supply the current to the transistor B (base) input pin. In your existing schematic you have a 100K resistor at the transistor input. So if you're trying to switch 1 Amp in the transistor output, you need at least 0.01 Amps (10 mA) at the transistor input. For a quick back-of-envelope calculation, a typical transistor might have a current gain of, say, 100. In the linked post, the beefier 2N3055 NPN transistor is proposed in place of the S8050. But start adding twists and turns and it reminds me of peeling layers of an onion - it will bring tears to your eyes! So doing an OGR search, there have been many threads about this circuit.such as this one. Appreciate any thoughts.ДЄt face value it seems like such a simple and low-cost circuit. These are rated at up to 5 amps collector current and 65 watts TDH. Overall it seems like a good little flasher circuit and I have ordered some test pcb's from OSH Park.ДЄs an aside has anyone got any ideas on how I might be able to use this basic circuit to alternately flash a couple of large 12 volt LED's, say up to 1 amp load? I have this vague idea that I might be able to use the low power alternating S8050 outputs to drive two larger NPN power transistors, sayВ TIP120's or similar. It is more affected by changes in supply voltage of course. The LED brightness is affected somewhat by trim pot adjustment, but not noticeably so. Interestingly the flash rate seems unaffected by supply voltage difference, at least over a range of 6-12 vdc. Flash rate is about 1 Hz or 2 seconds per complete cycle. I also reduced the C2/C3 values from 22 uF to 10 uF. With R3/R4 values of 100K, a trim pot of 100K seems to work well. Update: I have been experimenting with the trim pot idea suggested by Stan. This makes the timing dependent on the DC supply voltage though doing the math would be tedious to say the least! For the curious hard-core DIY'ers, at larger voltages this popular design (it seems to keep popping up) has the interesting property of momentarily turning the 2 transistors into Zener diodes across the reverse-biased E-B junction on each alternating flash.

If you are messing around on the bench and have a variable voltage supply, that might be another way to vary timing without using a trimpot(s) in place of or in conjunction with R3-R4. I notice you have a rather large variation in voltage range. Separately, this circuit should exhibit flash-rate dependence based on the voltage. For example if R3-R4 are 100K, a 50K trimpot should work fine.

If the single trimpot value is similar to or preferably smaller than the value of R3-R4, the circuit should behave. OTOH, if you're only looking for a small trim range, say +/-25%, you could use just one trimpot inserted between the junction of R3-R4 and the positive supply. C3 variations to get closer to 50% duty-cycle. But this actually can have an advantage in that you can 'trim' out any C2 vs. Sure, you have to make two adjustments nominally set to the same value. That said, why not use two individual tiny low-cost trimpots for R3 and R4. Presumably this is an infrequent or once-and-done adjustment. If size matters, I'd think that dual-gang trimpot is a tad large and somewhat expensive at 65 cents (that's more than the cost of all the other components).