MV-52B Tap Clock and 4022 question

[Slade]

Hi,
I have this MV-52B chip that must be supplied with a 5v regulator, and therefore delivering 5v pulses to a 4022 sequencer.
I want to use this sequencer to drive an led/ldr module. I've done this in the past with analog, not tap tempo, clocks with nice results, getting enough voltage to drive the led to get a very low resistance from the LDR, but now I'm stuck with 5v maximum for the led as the sequencer must be also supplied with 5v to actually operate with the tap tempo chip, so the led is getting a maximum of 5v that's far from the 9v I was getting with analog clocks.

What I tried was supplying the 4022 chip with 9v and using an opamp buffer with a gain x2 at the output of the 5v clock. It worked kinda good but I'm having troubles with the steps in the sequencer. I have a selector for 2,3,4,5,6 and 8 steps, and they all work well except for the 8 steps mode, where it jumps the first step starting on the second so I'm getting 7 steps instead of 8. I think it's because of the small voltage difference between the supply power and the clock voltage.

So, what would be the best way if there's any to make the 4022 supply 9v to the led from a 5v clock? Maybe there's something I'm doing wrong with my x2 gain opamp approach.

Regards,
Fernando.-

[duck_arse]

why not slip a transistor between the 5V clock output and the 4022 input? the collector resistor goes to 9V, the 4022 goes to 9V, and if you can stand the clock output being inverted, everyone is happy. if you have a spare inverter lying around the circuit somewhere, 5V or 9V, only matters which side the transistor you put it.

[Slade]

Thanks for the answer I'll make some tests.
Maybe I could also use a different approach that would be to put the x2 gain opamp at the output of the 4022, right before the led. Given it delivers 0v to 5v, the x2 opamp would get me from 0v to 8v-9v ideally.

[duck_arse]

you could put the transistor at the output of the 4022, and level translate just the led if you wanted to. ditch that op-amp!

[Slade]

Yeah, opamp doesn't do it! I'll try with the transistor.
What did you mean with the clock output being inverted?

[Slade]

The transistor between clock and 4022 doesn't do it. It's just the same as with the opamp.

[ElectricDruid]

The transistor between clock and 4022 doesn't do it. It's just the same as with the opamp.

Both proposed solutions should work. Duckarse's first suggestion of using a transistor as a level shifter between the +5V circuit and the 4022 running on +9V should be fine.

The alternative proposed, using an op-amp to provide gain to get 9V to drive an LED, should work too, but it's far too complicated for a simple LED driver. You could also use a transistor to make an LED driver on the 4022 output, with the 4022 on +5V, as Duckarse suggested second. That's probably what I'd go for.

But what I don't understand is: Why does this LED need 9V? Why not just run the LED at 5V? Reduce the LED's series resistor accordingly to get enough current through it, and off you go. If the 4022's outputs can't supply enough current, either use a low current LED (they'll manage 2mA, surely?) or go back to adding a transistor LED driver.

HTH,
Tom

[Slade]

Why does this LED need 9V? Why not just run the LED at 5V? Reduce the LED's series resistor accordingly to get enough current through it, and off you go. If the 4022's outputs can't supply enough current, either use a low current LED (they'll manage 2mA, surely?) or go back to adding a transistor LED driver.

Thank you for the input.
The led is already with a 100 Ohm series resistor. I'm using a ultrabright orange led. The led won't light up enough with 5v to make the LDR go low enough on resistance, so I need  more voltage for the led.
Both approaches do work until I go to 8 steps, then it becomes unstable.

[Slade]

Ok, a comparator between clock and 4022 did the job perfectly. Thanks, Rick (Frequency Central)!!!

[ElectricDruid]

Ok, a comparator between clock and 4022 did the job perfectly. Thanks, Rick (Frequency Central)!!!

Glad you've made it work.

With a 100R resistor and 5V, you've got 50mA going through your ultra-bright LED. That seems like loads to me, so I'm not sure what's going on there.

T.

[Slade]

Ok, a comparator between clock and 4022 did the job perfectly. Thanks, Rick (Frequency Central)!!!

Glad you've made it work.

With a 100R resistor and 5V, you've got 50mA going through your ultra-bright LED. That seems like loads to me, so I'm not sure what's going on there.

T.

Yeah, not sure also, but with 5v the led simply won't light enough to go really low on the LDR.
Now with 9v and 100R it gets as low as 1k.

PS: Have you sent me the sample chips?

[ElectricDruid]

Yeah, not sure also, but with 5v the led simply won't light enough to go really low on the LDR.
Now with 9v and 100R it gets as low as 1k.

PS: Have you sent me the sample chips?

Oh, Hi Fernando! Didn't realise it was you. Yeah, I sent you some chips ages ago...did they never make it? Should I try again?

Regards,
Tom

[Slade]

 
That's really bad, I never received them, I thought you had forgotten about it..
I feel bad asking you to ship them again. I got 2 more from Small Bear for some projects. I think I'll be soon contacting you to buy some more.
Cheers!