Continuity Tester Project

[MCU88]

Doing an continuity tester from scratch (never done one before) Any ideas, suggestions and or criticism on my schema?:

 

[MCU88]

Added clamping protection:

 

[MCU88]

Better the zeners for crowbar you think?

 

[chemelec]

Why don't you just use an Ohm Meter?

 

[MCU88]

Why don't you just use an Ohm Meter?

I am engineering a range of DIY KITs to sell. Some small simple projects like this (say a dozen) and some more complex projects say half.

 

[chemelec]

Well Even a Simple, Single Transistor circuit and a Buzzer, can be made for Continunity.
Works and Very Cheap to make, Just Doesn't Look Elaborate.

 

[JimB]

My first thoughts are about sledge hammers and nuts...

A more positive thought is:
Why not make a meter to measure low resistance, say less than 5 or 10 Ohms, and have an adjustable alarm point setting so that as you are "buzzing out" a cable or whatever, the thing will sound to tell that there is continuity if the resistance is less than some value set by the user, say 2 Ohms.

JimB

 

[blueroomelectronics]

I am engineering a range of DIY KITs to sell. Some small simple projects like this (say a dozen) and some more complex projects say half.

You might want to see what other kits are already on the market that do the same thing. Also it's a hard market to get a break in and your margins will be razor thin.

 

[Tony Stewart]

Doing an continuity tester from scratch (never done one before) Any ideas, suggestions and or criticism on my schema?:

If you want to succeed how you you know without a goal or spec?
1) Cost , not to exceed
2) Effort ( by you and end-user )
3) Your purpose? make money?
4) Tester Purpose ?
trace simple passive copper connections ?
find sliver shorts or almost opens ? ~ 100 mOhm? <1 Ohm?
User selectable? Conductance visible with several LED scale ? < 1, <0.1 < 0.01
Battery life? type?

Your design is is basically a rough current sink and no precision reference with a comparator and output magnetic buzzer and LED.
It could be made much cheaper and simpler if that's all you want to do.
Or you can add a bit more and do more with it.

But first decide what you want to do with a simple spec.

This design uses a 13mA CC sink with 0.65V/47R.

DMM's use about 1mA but measure voltage and display Voltage in Diode test mode.
There is no right or wrong numbers, but some are more useful.
Some are useful for tracing shorts and measure down to mV drops with higher current.

 

[MCU88]

Well Even a Simple, Single Transistor circuit and a Buzzer, can be made for Continunity.
Works and Very Cheap to make, Just Doesn't Look Elaborate.

Please post an schematic.

 

[MCU88]

Your design is is basically a rough current sink and no precision reference with a comparator and output magnetic buzzer and LED.

The circuit uses an multi-turn trimpot attached to an regulated power supply. What is wrong with the reference?

 

[MCU88]

You might want to see what other kits are already on the market that do the same thing. Also it's a hard market to get a break in and your margins will be razor thin.

I am talking about an actual 'real world' electronics shop. Not eBay and websites. Things are different in the 'real world' My profit margins would be textbook thick.

 

[NorthGuy]

Why not make a meter to measure low resistance, say less than 5 or 10 Ohms, and have an adjustable alarm point setting so that as you are "buzzing out" a cable or whatever, the thing will sound to tell that there is continuity if the resistance is less than some value set by the user, say 2 Ohms.

This is exactly what my Fluke does (among other things)! You can turn off the buzzer and read resistance values.

 

[blueroomelectronics]

As a kit it'll be a hard sell considering that even the cheapest multimeter has a continuity tester.

 

[MCU88]

As a kit it'll be a hard sell considering that even the cheapest multimeter has a continuity tester.

1. As an salesperson I would encourage people to buy and build my KITs for hobby and education
2. My continuity tester is programmable. 1R to say 1K ohm. Whereas most multimeters indicate valid continuity for measurements under 40R only. There is no 'fine tuning'

 

[MCU88]

You see things are different in the real world, unlike faceless people on the Internet (many of which are arseholes) A new customer walks into your shop, he / she is new to electronics, you make them a cup of coffee and start talking and an hour goes by and they feel obligated into buying something. You are new to electronics so I recommend this KIT for you. Don't forget about tools as well. I have a nice new multimeter here for you for $99 (my cost is $25) -- plus I have an beautiful soldering iron on special at the moment for $69.99 But if you are paying cash and purchase the both together then I can knock off 10% just for you!

 

[NorthGuy]

But if you are paying cash and purchase the both together then I can knock off 10% just for you!

Sorry, buddy, I've just ordered all this plus a bunch of interesting boards on eBay for $25 including shipping. But I'll be happy to discuss my circuits with you, so I'll drop by next week. Hope you'll have free cofee and doughnuts for me.

 

[MCU88]

Sorry, buddy, I've just ordered all this plus a bunch of interesting boards on eBay for $25 including shipping. But I'll be happy to discuss my circuits with you, so I'll drop by next week. Hope you'll have free cofee and doughnuts for me.

Don't get me wrong. I am not saying that it is easy money. I will be flooded with customers coming back with KITs that do not work because of poor soldering. Now to maintain a good business relationship with them and keep them coming back for more, what am I going to do about it? Do I offer to sell them an pre-built KIT at an discounted price? Do I give them on the spot lessons on soldering and sell them another one at an discounted price?

 

[MCU88]

Hope you'll have free cofee and doughnuts for me.

Yeah FREE coffee with truth serum in it. You just hit the floor or make an run for it if you are an paedophile.

 

[blueroomelectronics]

You see things are different in the real world, unlike faceless people on the Internet (many of which are arseholes) A new customer walks into your shop, he / she is new to electronics, you make them a cup of coffee and start talking and an hour goes by and they feel obligated into buying something. You are new to electronics so I recommend this KIT for you. Don't forget about tools as well. I have a nice new multimeter here for you for $99 (my cost is $25) -- plus I have an beautiful soldering iron on special at the moment for $69.99 But if you are paying cash and purchase the both together then I can knock off 10% just for you!

You have a brick and mortar shop? It sells coffee and kits, that's a first for me.

I bought a great little multimeter a UT61E and a Rigol DS1054z online, I purchase parts that way too. Maybe Starbucks will start selling kits.