Help with electronic components

[blfinche]

I'm trying to build the attached circuit, but I am having a hard time finding the parts at the local Radio Shack. Can anyone tell me what equivalent components that I can use from RS?

The components I'm having trouble finding are :

ZTX502 - A transistor?
LDR11K - What is this? A photocell?
CA340

Thanks,
Bobby

[blfinche]

Image

[HarryC]

I recognise Geoff Sleath's tachometer! ZTX 502 is a tranny, LDR1 is a light sensitive resistor (the bit you point at the prop), CA3140 is an 8 pin integrated circuit of some description. If you need more info or alternatives try asking geoff at geoff.sleath@btinternet.com

H

[blfinche]

Thanks. I'll send him an email.

Bobby

[steve lewin]

I'll move this to the Modelling Science forum since it's not about radios.

The ZTX502 can be replaced by almost any small signal NON transistor you have handy. I guess the CA3140 could be replaced with many FET input Op-amps but I don't know what you have available to you. You may have to change a few component values anyway depending on the characteristics of the LDR you use.

Steve

[blfinche]

Steve,
It may get more hits there, but it is about a radio. This circuit plugs into a Profi transmitter and provide a tachometer output on the display.

Bobby

[vintage1]

Corrections.

The LDR 11K is indeed a photoresistor. Sorry have no alternatives except ORP12 rings a bell...

The ZTX502 is shown as not a NON transistor, or even an NPN transistor, but a PNP transistor. It is entierly non critical and any small PNP will work.

The CA3140 is a standard 8 pin opamp and many will do - TL071 or in fact a 741 etc etc, except I suspect there is something about a 3140 in that its inouts can operate down near ground level.

I can't remember. Its an RCA part as specified. I must say that whoever designed this didn't go for 'industry standrad' components did they?

[blfinche]

vintage1,
I actually emailed the designer and he said he built it 8 years ago with what was on his bench. He indeed said none of the parts were critical. If I could source the parts locally, I was going to build it. With my limited electronics knowledge, I'm not comfortable changing out parts, since I don't know what they do. I guess I need to get a book on beginning electronics. :)

Bobby

[Bruce Abbott]

As Vintage1 suspected, the CA3140 cannot easily be substituted. This is not a problem however, as it is readily available. 2N3906 is a popular PNP transistor that can replace the ZTX502. I chose a low resistance CDS sensor which should work well in bright sunlight.

The following parts are available from Jameco (http://www.jameco.com/).
CA3140E, Jameco part #12204
CDS001-8001, Jameco part #202403
2N3906, Jameco part #178618

[blfinche]

Thanks Bruce. I will check those out.

Bobby

[vintage1]

Yeah. My memory served me abpout roght on te CA3140. Its a mosfet input op amp that can run with the inputs at or near ground level.

Govcen what that circuit does, and teh fact that you really don't need anything that clever, I'd say a TL071 would do with possibly a resistor on the input up to rail to bias it into a sensible area.