Laboratory Equipment

If you are intending to design and build a coilgun then you will need some sort of test equipment. The absolute minimum is a multimeter. Cheap digital multimeters are excellent value so there is no excuse - buy one. Higher spec meters will have additional functions such as transistor testing, frequency or inductance measuring etc. You will need some sort of meter to assist you in building and debugging circuits.

A multimeter will get you quite far but if you are serious about coilguns or electronics in general then you should seriously consider a digital storage oscilloscope. This lets you capture and analyse transient events such as the coil current waveform or the triggering pulse etc. A bench top DSO such as those made by Tektronix will cost you over $1000 but there are cheaper alternatives. A PC based DSO is worth considering. Older versions of these 'scopes plug into the PC's parallel port, but the latest models have USB connectivity. You can also get a tiny 'scope that plugs directly into a USB port - USBScope50. All the functionality of a standard scope is available via the virtual instrument interface. You can also save the raw data (as a .txt file, or possibly other formats such as .csv) or a screen shot of the trace. The cost of this type of kit is around $400 upwards. If you're really serious then you could go for a data acquisition card which can offer multiple input channels with programmable gain and 12 or 16 bit resolution. With these cards you can write a programme to sample the various channels and display the data as you see fit. This is something for the hard core electronics fanatic. Something to note with data acquisition equipment is the sampling rate. The absolute minimum rate you should consider is 200KHz, this will allow you to measure transient events of 250us with 50 data points of temporal resolution. The 12 bit cards which run at around 200KHz are not too expensive, coming in at around $300. Expect to pay well over $1000 for a 16 bit card capable of 20MHz. As well as PC based scopes there are handheld scopes and graphical multimeters. Handheld scopes from the 'big' manufactures will cost you an arm and a leg, however, there is at least one manufacturer which produces a cheap HH scope for the hobby market. This costs around $200 and it can be connected to a PC and the data downloaded and displayed.

Bear in mind that you tend to get what you pay for. Most equipment aimed at hobbyists will perform adequately but won't compare favourably with high quality equipment. For example, take the PC DSO I own, it functions well and does all I have asked of it - so far, but compared to one of the compact bench DSO scopes from Tektronix, it doesn't stand up.

You might also want to get a prototyping board. I find this a great help when designing and debugging circuits.

Here is a list of my Lab equipment:


PSCH1000 Capacitor Charging Power Supply -

I've been wanting to make a 'proper' capacitor charging power supply for a while and eventually got around to making one. This system is rated at 1000 V maximum output voltage at 100 or 50 W (selectable) nominal output power (this is a constant power charger as opposed to constant current). After turning on the mains the Enable button must be pressed to activate the high voltage stage. The output terminal is a "safe" type high voltage BNC connector on the rear panel. An Inhibit input terminal (BNC) allows the supply to be either temporarily inhibited or disabled (requiring the Enable button to be pressed to operate the supply again). The inhibit period is controlled by the pulse width on the BNC connector. The inhibit is useful if the load capacitor gets discharged through a latching type switch such as an SCR, where the current must be allowed to decay until the SCR turns off.

The supply is based on a flyback topology and uses an ETD59 type core kit. Switching operates in current mode control with a fixed off period. The flyback topology is naturally short circuit proof but overvoltage protection circuitry is included which disables the supply if the output exceeds 1200 V (this protects the supply but not the load capacitor). If the external circuit has the potential to ring then a reverse biased clamp diode (with perhaps a dissipative resistor network) needs to be placed across the load capacitor, otherwise the flyback rectifier diodes would experience a high current surge as they are forward biased by the negative voltage of the ringing current.

Fluke 189 Multimeter -

This is an excellent meter that is capable of making highly accurate measurements. It can store data in memory for later reference, or for download to a computer via an infra red link. A backlite for the LCD makes the meter easy to read in low light conditions. The meter can be used to read currents of up to 20 A for brief periods.


TTi Pulse Generator -

This generator is specifically designed to produce pulses. It can generate single or double pulses with a large variation in mark/space ratio. The pulses can be triggered manually, by a gating pulse, or can run continuously.



This instrument can make accurate measurements of the parameters that coilgunners like to know; namely inductance, capacitance and resistance. The dissipation factor measurement allows the ESR of a capacitor to be determined. Similarly, the Q factor measurement can be used to calculate the resistance of an inductive coil. All measurements can be conducted at either 120 Hz or 1 kHz, to best reflect the actual operating frequency.


Atlas ESR Meter -

A compact meter for measuring the capacitance and the effective series resistance of various types of capacitor. The instrument operates with a test frequency of 100 kHz.


White Gold DMM -

This is a good quality meter which can measure frequency, inductance, capacitance and perform transistor testing in addition to the standard voltage, resistance and current. It has the capability to measure currents of up to 20A for short periods of time.


Black Star 100MHz Universal Counter Timer -

A counter timer could be considered a luxury item since most timing measurements can be accomplished using a DSO. However if many different simultaneous measurements are required then additional equipment like this becomes an advantage. This is a precision instrument and it get used for 'special' measurements.


P255 Pulse Timer (Own Design) -

Considering that the Black Star instrument is quite expensive I decided to make a cheap and cheerful version of my own for every day use. This is a very basic timer which has three ranges 2.55ms, 25.5ms and 255ms. It accepts a TTL compatible square pulse, triggering on the positive edge and stopping on the negative edge. It is based around a PIC16C84 microcontroller which has electrically erasable program memory - excellent for prototyping work. The latest devices use flash programme memory - PIC16F84.

If you don't have a microcontroller programmer then you could build a timer based on standard digital ICs. There is a great description of such a timer at the Magnetic Gun Club.


Velleman 32MS/s Dual Channel PC DSO (Kit) -

A DSO is an essential piece of equipment for detailed experimental work. At 32MS/s there is sufficient temporal resolution to analyse very short transient events (by coilgun current pulse standards). It comes as a kit and builds quite well. Calibration can be a little annoying since the trimmer components are very basic.


Pulsar V1.0 Square Pulse Generator (Own Design) -

I designed this little pulse generator as a general purpose tool. It can output a square TTL compatible pulse with widths from 1us to 100ms in 16 discrete steps e.g. 1us, 2us, 5us, 10us, 20us, 50us, 100us etc. It is based on a PIC12C509 microcontroller. The pulse width is selected via a 4-way DIP switch.


Velleman 30V @ 10A Bench Power Supply (Kit) -

A nice piece of equipment which has a current limiting facility. It can't power a coilgun directly but it is useful for charging batteries and capacitors as well as powering prototype circuits.


Powered Prototyping Board (Own Design) -

This is a basic board with +/- 15V supply @ 500mA per rail. It's always a good idea to prototype a circuit before committing the design to PCB. A case in point is the P255 timer I designed. I must have had the microcontroller in and out about 10 times trying to debug the firmware.


Velleman HPS5 Handheld 'Scope

This instrument is a very useful piece of equipment having most of the functionality of a standard 'scope. Since it is battery powered it can be used to perform floating measurements on parts of systems so long as the floating potential isn't excessive - a few tens of volts is fine. If I have doubts about making measurements on the PC based 'scope then this one is put to use. Better to blow a £120 instrument than a £1000 computer.

Two things that are 'missing' from this 'scope are an adjustable trigger level and an I/O port. In order to trigger on different voltage levels of a waveform, the vertical position of the waveform needs to be shifted. This can mean squeezing the waveform into the upper or lower half of the screen to trigger on the lowest or highest parts of the wave. An I/O port would be useful for permanent storage of data. This feature seems to have either been abandoned or is intended for future versions of the instrument (there's a blanked off I/O hole in the case)